Hello.
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I understand that you have moved/deleted all the TeamViewer Application and system files by moving them to thrash and force-shutdown the computer and not able to boot it up again and getting an error saying "SecurityAgent was unable to create requested mechanism TeamViewerAuthPlugin:start."
I would like to let you know that you are not supposed to Uninstall TeamViewer like that. The recommended method to uninstall it is:
1) Open the TeamViewer app and click the TeamViewer menu in the top-left corner, then click Preferences.
2) Go to the Advanced tab.
3) Scroll down to the very bottom and check Also delete configuration files
4) Click the Uninstall button.
5) TeamViewer is now uninstalled.
This issue can be caused by deleting an authorization plugin on macOS (in this case, TeamViewerAuthPlugin.bundle) without de-registering it first. It is recommended to uninstall it through the above process . This makes sure that the plugin is properly de-registered before deletion.
The way you have moved the TeamViewer application files and configuration files does not properly de-register the authorization plugin.
If you do not have the possibility to restore the plugin by Installing TeamViewer on another Mac and copying the authorisation file into the correct path through Terminal in macOS Recovery, you may instead be able to delete your Mac's authorization database. Your Mac re-creates a missing database during the next startup (using some default settings that are fine for most users).
Follow these instructions
1) Start your Mac in macOS Recovery by holding down Cmd-R until the Apple logo appears. Once your Mac has booted into macOS Recovery, you should see a window titled "macOS Utilities".
To delete the authorization database, your Mac's hard disk needs to be mounted and you will need to know its name (usually something like "Macintosh HD" or "macOS").
2) Open Disk Utility and check the left sidebar for the name of your disk. For Macs running Catalina, look for the name that does not end in "- Data". Select the disk in the sidebar. Click "Mount" in the toolbar (if you only see "Unmount", it is already mounted and you don't need to do anything). Now, Quit Disk Utility.
3) You should be back at the "macOS Utilities" window.
4) From the menu bar on top of the screen, open Utilities > Terminal.
5) Enter the command
rm "/Volumes/<your disk>/var/db/auth.db"
6) Replace <your disk> with the name of your built-in hard disk, e.g.
rm "/Volumes/Macintosh HD/var/db/auth.db"
Make sure not to forget the quotes in case your disk name contains spaces.
7) Restart your Mac.
8) The computer should be functional .
As, I said that you may or may not have the possibility to restore the plugin by installing TeamViewer and copying the authorisation plugin file to the other Mac and copy it into it with terminal, I am describing that method too If you want to try it out. Attached in additional text as I have crossed max. Character limit of 5000. The character " Â " is being added somehow and I am not able to remove it Please ignore that character in the additional text below.
Hope it helps you and problem gets resolved and you are going to be able to boot into your Mac again.
If you need any help please reply back and I will try to help you out.
Cheers!