There is an issue with the UGC endpoints returning “Internal server error”. Not sure when this started, but I would guess after June 20.
You can simply test this out by going to the online console for testing api calls and try out UGC/Halo 5 Player Game Variants (<343 Industries> developer portal) or UGC/Halo 5 Player Map Variants (<343 Industries> developer portal), provide a gamertag, and SEND (see below). Also, if you try to get the name of a specific map variant from UGC/Halo 5 - Player Map Variant (<343 Industries> developer portal), it will return “Internal server error”.
Additionally, UGC/Halo 5 Player Game Variant can’t be tested from the console for a specific game type (unless you already have the mapvar id and owner gt) because, as of now, the owner gamertag is not provided when you run Stats/Halo 5 - Match Result - Custom.
UGC
Halo 5 - Player Map Variants
“statusCode”: 500,
“message”: “Internal server error”,
“activityId”: “3f4e1a63-4a74-4287-86a1-adac3b3de2b0”