So I am making a map in forge and when I try to open it in the forge/customs lobby it just says retrieving data. I left it running for ~20 mins and still nothing so I figured it would never load. In forge I am able to start the game anyway but in game I can only ‘Save Map’ and not ‘Save Map As’ (I get ‘Saving…Failed’). In customs it still says retrieving data but I cannot start the game. All of this only happens with this map - I can load all the others find.
Turns out I just hadn’t selected a game mode which is why I couldn’t start the game in customs. The save error still exists though. I have tried hard booting my Xbox but that didn’t work
I’m having the same issue. I just spent 10+ hours on my new map and now it won’t even load… 343 needs to get their stuff together because this is annoying. Game is so buggy that it’s ridiculous. Well put together 343, GJ.
I am getting the same ‘retrieving data’ message. I am still bale to work on it and quick save in forge but the map is not loading correctly in custom games. I am 95% finished after working on it for a week, so this is very frustrating!
I am having the same problem 
Sign out of your Xbox live profile sign back in and give halo about 1-3 minutes to load your data (req points,Spartan rank etc). Hopefully this will resolve the issue your having if not I’m sorry 
as it could be frustrating especially when in forge