A Required Download is Missing: El Capitan 10.11.6 - - also Photos quit unexpectedly while using the Slideshows plug-in

Hi ASTRO24,

Thanks for the reply. I have checked and verified that the hard drive is ok via Disk Utility as well as the Diagnostics test which verified the hard drive and all hardware. I have entered macOS recovery several times but always with the same failed results. I've used every trick I could find on these and other forums to no avail. Why should this have to be so hard?

I have not reloaded the original OS that came on this machine and really don't want to go that route and don't want the latest OS available that will run on this machine, I simply want the same OS (El Capitan) that I am currently running, reinstalled so it over writes the current one and hopefully fixes the Photos issue which I believe was from a bad install previously.

Yup, been there, done that, it too failed. It let me load Lion but once loaded, Lion would not let me past the login screen, it kept rejecting my password. The Apple Tech asked if I may have used a diff password back when I was running Lion, I checked my files, the password was the same as it is under El Capitan and that matches my memory as well.

If I wipe my drive again and restore from my TM backup, I'm only going to get the bad install of El Capitan and my Photos will not load due to the error stated in my first post ("Photos quit unexpectedly while using the Slideshows plug-in"). Seems I'm in an endless loop and can't figure out why. I have, in the past, been able to reinstall El Capitan without issue, something has changed but I don't think its on my end. I may have no choice than to use Internet Recovery and install High Sierra as I'm getting pretty tired of going in circles. Thanks for your clarification and reply. Just trying to keep this machine alive and well till Apple releases the 16" MBP with the Apple M1x chip.

ASTRO24, I get that and that is what I was trying to do. No way its allowing me to reinstall El Capitan no matter which recovery method I try and I have tried them all. CMD-R, CMD-Option-R, via a USB boot disc, setting the internal clock back and then trying those methods, nothing has worked. I either get the “A required download is missing” or “Cannot be installed” depending on which method I use to try installing it.

Eau Rouge, I did that, several times using a few diff dates, all prior to Jan 2019. I did download the installer from the page that your link takes me to and I did make a bootable USB disk via the Terminal app. Once I was booted to the USB installer disk, I did as you wrote in your reply but still got the error that a download was missing.

Folks, I have given up, I just used the internet recovery method and installed High Sierra because I needed to have my system back and was going insane running in circles with an attempt to reinstall El Capitan. Once High Sierra was installed, the only two issues I had were that all my local mailboxes were missing and one of the Microsoft Office apps did not work (Word). I reinstalled Microsoft Office and that fixed Word and I manually recovered all my local mailboxes so at this moment I am back to a running system, albeit not the OS I wanted.

Thanks for your suggestions, I certainly appreciate the fact that anybody chimed in on this old software issue

I was connected to my router via Ethernet but am sure others were using their connected devices during my trials. Why is that important? I too have downloaded and successfully installed El Capitan on this iMac a few times in the past but this time it just did not want to cooperate.

Ahhhh, was waiting for that question :-) My iMac is 10 yrs old, over the course of that time, I've had a few issues with a corrupt hard drive (unknown root cause), corrupt backup drive (unknown root cause) and OS upgrades gone wrong. In these cases, I wiped the hard drive and rebuilt from scratch but always loaded El Capitan back on it because I like its robustness, simplicity and I have had issues when upgrading to High Sierra which is the latest OS this iMac can take.

This last issue was that when I would put the iMac to sleep via the Sleep button from the Apple menu, 40-50% of the time it would go to sleep only to reboot a few seconds later, not just wake up, but a complete reboot. I watch the screen go dark, I can hear the hard drive writing and then go quiet and since I have a second monitor connected, I can see when it powers that monitor off and all goes completely dark and silent. BUT, one or two seconds later I can hear the hard drive spinning up, I get the chime, the screens light up and the reboot process begins. This just started happening out of the blue.

So, thinking I might have an issue with the mouse in that the Restart button is just below the Sleep button, I set Energy Saver to put it to sleep, so I just walk away and 10 minutes later without activity, it puts itself to sleep. However, by then I'm in another room but can hear the startup chime. I come back only to find it in the reboot process, again 40-50% of the time.

In my efforts to troubleshoot this, including a few calls with Apple Support on the phone, we decided to reinstall the OS since all hardware testing showed nothing was wrong. I was in fact able to reinstall EL Capitan but only after wiping the hard drive and then once it was installed, Photos started crashing, so I thought I simply had a bad install and would just reinstall it again. This iMac is alway connected via Ethernet. However, I could not manage to reinstall it like I did the first time and that then put me down the path of trying but failing to reinstall El Capitan. Also, during this time, I saw a few kernel panics and for some unknown reason my backup drive changed from read/write to only read so TM could no longer back up to it.

Disk Utility would sometimes see the backup drive and sometimes not see it, same of course with Finder and when Disk Utility would see it, it could not repair it, (First Aid would fail to repair it). Upon subsequent hardware tests (restart with the D key pressed), it reported an issue with the internal hard drive....4HDD/1140000004:SATA(0,0). So upon investigating that, I figured this hard drive had seen better days and I need to replace it. Yet, upon the next hardware test, including the extensive loooong running one, it passed. Ok, it could still be the hard drive sending early warning signals but I once again turned my thoughts to the OS since somehow my backup drive got corrupted and Photos app kept crashing (even in Safe mode).

I wiped the backup drive which took care of the read only issue, made a new complete backup and then unplugged it from the iMac while trying to reload El Capitan, just figured a complete fresh start was what I wanted to do and then I would once again run the hardware test. The kernel panic went away somewhere in that process and when I gave up trying to reload El Capitan and used Apples Internet Recovery and loaded High Sierra, I reconnected the backup drive, made a backup, then rebooted with the D key pressed and ran another hardware test which passed.

I then thought I was in good shape as everything was working well but I can't leave well enough alone when I don't know root cause so I rebooted once again and ran the hardware test and the same hard drive error appeared. So today I will go in search for a replacement hard drive, maybe go SSD as I seem to recall an SSD kit on iFixit a while back that had the temperature connector so the fans would operate correctly.

Anyway, I'm sure I left a few bits out and probably some of that is out of order but that's the gist of it :-)