Visual Studio Error List is hidden

Just Type:

CTRL+\+E

(without the + sign)

In my case VS2015 was finding errors but wasn't displaying what are the errors, basically Error List tab was empty. But checking Output tab i found errors and clicking on them opened up the file which had errors, also errors started to show up in Error List tab as well afterwards.

That's a new one for me.

Go to Tools > Import and Export Settings and export all your settings to a file for safe keeping.

Then go in there again and reset everything. Report back if that helped. If it did, try importing your settings again to see what happens.

Window > Reset Window Layout