Individual user in Citrix VDA environment was using Teams just fine one day and the next had error 0x80070003. No updates/patches/changes of any sort. Uninstall and reinstall of Teams (Appdata location), and clearing of Teams cache in the user profile did not resolve the issue. Found this script in a forum that fixed the issue:
Create this batch file and run
attrib -h -r -s %appdata%\Microsoft\Teams /s /d
rd /s %appdata%\Microsoft\Teams /q
attrib -h -r -s C:\Users\%username%\AppData\Local\Packages\Microsoft.AAD.BrokerPlugin_* /s /d
FOR /D %%i IN (C:\Users\%username%\AppData\Local\Packages\Microsoft.AAD.BrokerPlugin_*) DO RD /q /S "%%i"