Memory RAM disappears instantly

Yeah, don't believe anything an IT department says, CleanMyMac is one of the wort things you can install on your mac.

Go to the developers website and get the full uninstall instructions, simply deleting the app is not enough as that will leave active elements on your mac.

Macs do not need any apps that claim to clean, optimise or otherwise improve the performance of your mac, the mac does a fine job looking after itself. Apps like CleanMyMac often flag up files as threats which you may be tempted to delete, often these files are needed system files that if removed will lead to the meltdown of your mac.

The same goes for an anti-virus apps, there are no viruses that affect the mac.

You may want to read this, https://discussions.apple.com/docs/DOC-8841

From what you wrote it sounds like one or two of your RAM modules may have expired, this is unusual

but not impossible, when you bought the mac did you have all the RAM installed by Apple or did you

buy after market RAM to get to 40GBs. And if you did buy after market RAM did you get some form of guarantee.

Some offer lifetime guarantees.

I would open the mac up and take out the aftermarket RAM modules and see if the mac runs happier with the original Apple RAM left installed. If it does then you may consider buying replacement modules to get the RAM back up to 40GBs.

Install memory in an iMac - Apple Support

To check if your installed RAM is being recognised by your mac click on the top left of your screen

and select About This Mac, now click on Memory.

The window will now show which of your Memory slots are being recognised/ used and the size of the memory module

installed in each slot. If you see less than 40GB installed then you have a problem with one or more of your RAM modules.

You can also look at the Activity Monitor app in your Applications> Utilities folder. click on the Memory tab.

This will now show you what is using the Memory on your mac. There is a Memory Pressure graph at the bottom of the

panel. It should be green indicating everything is fine, amber shows the memory used is running high but not critical.

If it it goes into the red then there may be problems, save all your work, quit your apps. Restart the mac.

Open your apps one by one and the files you were working on, keep an eye on the memory pressure to see if it goes red again, if it does then that might be an indicator that one or more of the modules has a problem.

If you do find you need to replace any of the memory modules then you must replace it with the exact type of memory

module(s) for your specific model and year of your mac.

Online memory resellers often have scanners that can identify your exact model and

give you results for the correct type of RAM your mac requires. There will also be manual menu selectors.

First uninstall CleanMyMac. It is considered "junkware" by experienced users and is known to cause any number of problems.

You're welcome. Also…

Install EtreCheck and post the report. Allow Full Disk Access.

https://etrecheck.com/

Use the Additional Text icon to paste in the report.

As already noted, cleanmymac is BAD.

Even if you uninstall it completely, as instructed, it may have already damaged your mac.

Very often a clean install is required to restore sanity to your mac.

But despite that: having only 28MB of RAM "free" is not a problem by itself.

The OS uses all the RAM it has available, and just having free RAM does not help.

That Etrecheck report, with full disk access, as dialabrain requested, may show other issues as well - but since you used cmm on this machine... a clean install may ultimately be necessary.

You're welcome.