(and so everybody is aware there is one other post today about a similar mcDSP plugin issue
http://duc.avid.com/showthread.php?t=406397)
Do you have your plugins licensed by the iLok key or iLok cloud? I know mcDSP does both, not sure about others. Are they subscription (expiring when?) or perpetual... Even say if you have a perpetual license make sure there is no other iLok connected or cloud license being used that may have an expiring mcDSP subscription license... Not that you should ever get that error but I am just looking for anything that could trigger some behavior to change at a time, like an expiring mcDSP license.
What does ILM show you for those exact plugin.. can you post a screen shot? Also include your ILM version.
Like you I would have first suspected the plugins, which I know you tried reinstalling. Did you do that from a clean download of those installers?
To be super paranoid: Reboot your Mac. Test Pro Tools runs at all, you only see these same errors. Quit Pro Tools. Move the .aaxplugin files for any plugins causing there errors out of the plugin folder (/Library/Application\ Support/Avid/Audio/Plug-Ins) , do a careful trashing or preferences using Peter Gates utility, trash *everything*. Then start Pro Tools and make sure you do not see any other errors, or strange behavior, except maybe a missing plugin warning. If so then download *a full new installer download for those plugins and install them. Start Pro Tools and then see if the problem is still there. (I want to avoid the case where those plugins were always corrupted but that is just now causing problems).
If you try that and still have the same problem and nobody else has better ideas I would try moving those licenses to a different iLok 2 or 3 and having that attached and testing.. or move those licenses to the cloud to test.
Make sure you do not have automatic updates on for *anything*.*macOS, Pro Tools, plugins etc.
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Not really going to help here, but since the 64-bit plugin thing cam up... you can always use the macOS "file" command to check if a plugin is at least trying to be AAX-64, but this in no way tells you that the plugin will work correctly or is not corrupted... just that the developer has tried to include 64-bit code in the plugin. You need to run file on the actual executable hidden inside the .aaxplugin bundles (that are just directories if you use a command shell on the Mac, like Terminal).
$ cd /Library/Application\ Support/Avid/Audio/Plug-Ins
$ file */Contents/MacOS/*
Will return a list of of the architecture support for every plugin installed on the system. i386 means 32-bit, x86-64 means 64-bit. Quick, who can write a script to make this show plugins with 32-bit only, 64-bit only or both support?
