The clients anticheat protection is not active (null client)

Vincentknigh  From what I can understand, the error is indeed caused by the EAC itself having issues, (so reinstalling and/or repairing it was a good call), but since that didn't seem to help, I do have a few suggestions that might:

1. Reviewing this EA Help article on how to troubleshoot the EAC, (it is a repeat of what you've already tried, but its still worth a look).
   
   You should be able to follow the steps for uninstalling the EAC for Apex and then run a file verification check for the game, (which should reinstall the EAC). It also might work best if you select to uninstall every instance of the EAC, and go for a completely fresh reinstall, (but if you play games like Fortnite, you would have to reinstall and/or repair those games or reinstall the EAC itself for each game).
   
   I did find under "C:\Program Files (x86)\EasyAntiCheat" the exe file "EasyAntiCheat", which when ran had prompted the user control menu, and then after clicking on the "allow" button, it popped up the repair service:
   
   

   I'm not sure which game number goes to what game, but for me, I only have 3 games installed that uses the EAC, (which would be Apex Legends, Fortnite, and Sea of Thieves), so in this instance, I could just reinstall each game.

2. As you've mentioned, you've already tried updating everything, running in admin mode, uninstalling/reinstalling, etc., but something else you could try that you haven't listed yet, would be to repair the system's files as there might be some corrupted files that's preventing the EAC from running properly.
   
   

   To repair the system's files:

   • Open the Command Prompt in administrator mode
     
     
   • Type, "DISM /Online /Cleanup-image /Restorehealth" (without the quotes), and wait for it to finish.
     Note: DISM stands for "Deployment Image Servicing and Management tool". It often repairs Microsoft related files, such as issues with Window apps. Some problems with the next file checker can only be fixed after running this one first.
     
     
   • Now type, "sfc /scannow" (without the quotes), and wait for it to finish.
     Note: sfc stands for "System File Checker". This one will repair system files, (such as important Windows drivers).
     
     
   • Lastly, restart your PC.
     
     
3. Another possible reason for why the EAC isn't running properly, (or at all), could be caused by interference by other programs. If any program is causing Apex to crash or to not fully load properly, those programs must be closed prior to launching and while playing the game.