Cannot install macOS Sierra on late 2015 IMac

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Cannot install macOS Sierra on late 2015 IMac

Hello Everyone, I’m so lost and truly need help. I’ve read multiple forums for hours and everytime I get past a roadblock another one appears.

I recently bought a late 2015 21.5-inch iMac from somebody. When I turned on the iMac for the very first time, it made me sign into a guest account (previous user reset it and created guest account). I was able to do so successfully. However, I had issues connecting the mouse via Bluetooth to the iMac (I was able to open Bluetooth settings, find the mouse but when I’d highlight it and press enter it wouldn’t try to connect to the Magic Mouse (it runs on batteries so I could not try connecting via usb). The keyboard and the Magic Mouse both work (I was able to successfully use them on my MacBook Pro). Because I was not familiar with keyboard shortcuts to bypass having to use the actual enter key, I decided to reset the iMac via internet recovery (it’s the default recovery option when pressing command-R upon start-up) with an internet cable. Initially I tried running disk utility but it said “First Aid found corruption that needs to be repaired. To repair the startup volume, run First Aid from Recovery.” Which was weird bc I was in recovery mode. So at this point I decided to give up and just restart the iMac normally however it would go to a flashing box with a question mark error -2100f.

At this point, I realized I needed to learn how to use my keyboard as a mouse so I learned how to use voice over commands. I then tried restoring from my external drive which I use with Time Machine on my MacBook Pro but the external drive wouldn’t show up. I am assuming because this is a vintage iMac and it will not be able to operate Ventura nor recover from it. I also tried installing the macOS Monterey but it wouldn’t install in either Macintosh HD-Data-Data-Data-Data-Data nor Update.

So I then ended up erasing the internal drive labeled “APPLE SSD…” with Guid partition map and I chose Apfs as the file format. However when I then tried installing the macOS, no

Hard disk would show up for me to select. So I went and tried to create a partition under “APPLE SSD….” But the +/- button was grayed out and then I realized its because there was no container disk underneath it. (Also, I noticed it was no longer “install macOS Monterey” but “install macOS Sierra”. )

I then tried erasing the internal disk again and this time formatting it as macOS extended (journal) and I enabled journaling as prompted when trying again to install macOS on a hard drive (none showed up). At this point after enabling journaling, there was finally a hard disk to install the macOS to. BUT it failed and asked me to try again. When I run disk utility, everything checks out and it says complete.

I tried starting in safe mode, I couldn’t get it to do so. I tried running diagnostics but my keyboard keys wouldn’t register so I couldn’t click “I agree”.

I don’t know what to do, please help me install the macOS, I do want to install macOS Monterey if possible since that’s the latest software I should be able to update to. I don’t know if I did something wrong with the internal drive. (I finally got a usb mouse to not have to use voiceover etc).

what do you think the problem is? What should I try next?

Posted on Aug 13, 2023 7:20 AM

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Johnb-one

Level 6

9,156 points

Aug 13, 2023 8:55 AM in response to nadashda

Hi, nadashda (hope I spelled that correctly)

+1 to the good advice posted by den. thed...use a USB wired keyboard and mouse and plug that into the Mac....Bluetooth mice and keyboards can be flaky/iffy/troublesome on startup or for troubleshooting...pretty much any USB wired keyboard and mouse will do (could be "Windows" or "Mac" doesn't matter....I'd also suggest you a reset smc/PMU followed by 3-4 Pram zaps on startup, as per this link: https://www.macworld.com/article/224955/how-to-reset-a-macs-nvram-pram-and-smc.html...with a USB wired keyboard and mouse your keyboard keys should register fine for safe mode and running Apple Diagnostic... (by holding down the "D" key on your keyboard on Startup.) .. startup in Recovery, either Internet Recovery or General Recovery (by holding down the Apple/command/Cloverleaf + R keys together on your keyboard on startup) . Pick a language and continue.... to Access Disk Utility, Terminal, etc, move your mouse/cursor to the top center of your screen and click. You should see Mac OS X Tools) . Disk Utility should be available, and then run it.....maybe Disk First Aid... I presume there's nothing on this late 2015 iMac that you want to try to save/salvage, you just want to start from scratch. I see, by your posting that you have an external drive with Time Machine which is great...that's very smart of you to have that and use it regularly, a very good idea. It looks like your main storage drive (*the Apple SSD) is OK (at least I hope so) ...so I guess that's it....Mac OS Sierra---->Mac OS Mojave or whever--->>and if your Mac meets the requirement for Mac OS Catalina, install that... please note that Catalina breaks all 32-bit support. All Apps/programs/software must be 100% 64-bit and Catalina compliant/supports Catalina....so, that's it from me...

John B

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