I've had this problem with every other updated MG map and fortunately I do know how to fix it however, it requires you do it manually every-time you encounter the problem.
If it says "Missing map/Error Blah Blah" you go into console on main CS:GO menu and copy the "https:---------------.bsp (or bsp2)" (one of them will require you take it out of the folder) and put that link into your Url bar. After doing so (in my case Chrome) it should auto download from our databases. Go into your Cs:go Property folder in steam/maps, and drag the .bsp(2) in that folder (replace an existing file if prompted) and VIOLA it Should download the map!
I hope this helps you out and good luck Gamer!