I've played the game normally for the past few years but today I attempted to subscribe to some of the modded zombies maps in the workshop. I have uninstalled 3 times and attempted to verify the game cache several times.
I have also unsubscribed and uninstalled all the maps from the SteamApps folder.
Tried searching around online for a few hours with no luck following what others say to do.

Please help, much appreciated.

Maybe you clicked alot of custom mods for download and they havent downloaded, wait for them to download and install then everything should be fine