From the stacktrace
EPiServer.Shell.Modules.ModuleFinder.GetModuleInDirectory(String routeBasePath, String moduleResourcePath, IEnumerable`1 configuredAssemblyNames, AutoDiscoveryLevel discoveryMode, String configuredName) +486
it looks like you have problem with modules/protected folder, probably missing/corrupt files.
Hi Alex, increase your logging level, use info or debug. Info should be enough because then you would get the log message what the the module finder is trying to load (so you know what module causes the issue). So depending on how you have the solution logging currently setup in episerverlog.config file, if you have the default then comment out the 'threshold' inside the errorFileLogAppender or change its value to info or debug, then also change the 'root' elementslevel value to info or debug. Restart your IIS or IIS Express and re-run the app to see what module fails from the log messages.
Also as the orginal exception comes from the creation of the module but passed in argument is null, this simply could be an issue that after the upgrade your IIS is loading a cached version so delete everything from your apps bin directory and re-build and run - might just work. Also if that didn't help, you could delete the temporary asp.net files (default location C:\Windows\Microsoft.NET\Framework\v4.0.30319\Temporary ASP.NET Files or C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files).
Probably a missing .zip file in the modules/ folder after upgrade. Double check you have commited them all to Git after upgrade and merge etc. You can always install an empty alloy site of the same version and check what .zips you need to have there.
What you can do is to reinstall all packages which would fix the corrupted or missing packages.
Note that the OP has reported that he fixed the problem, but that post contains spam links so I had to delete it. I kept this thread because it still has value for future visitors
I'd suggest reviewing your Git Ignore file to ensure the modules/_protected folder is not ignored.
Otherwise you have to do a git force push which often gets missed on check in after an install.
I have upgraded cms from 10.10.4 to 11.20.3. Also I upgraded data using updateDatabaseSchema="true" in web.config file.
Now I am getting below error. Please suggest.