Uhm this may sound like the go-to IT respond and dont mind it, but try first restarting, fully exit and reopen and see if that helps.
Otherwise try this, Go to Steam > Settings > Downloads and then Click "Download Region" and change it to a different one (any other city/country). Steam should restart after that. Try pausing the downloads now, it should work. You can always change your region back afterwards.
Hope this helps.