Gmod Server "CModelLoader::Map_IsValid: 'maps/<mapname>' is not a valid BSP file"

[PeterChamp]

Hello,
When I recently updated my gmod server and attempted to start it and run a map I got the following error: CModelLoader::Map_IsValid: 'maps/ph_kleiner.bsp' is not a valid BSP file map load failed: ph_kleiner not found or invalid
I found this strange and tried using a different map, but the same error came up, this time with the new map's name. I then changed the map to gm_construct and it worked with no errors. I am looking for help fixing this error so that I can use custom prop hunt maps for my server instead of having to use the default gmod maps. Any help would be greatly appreciated!

[Tenrys]

Simply means the map is invalid or doesn't exist. Put it in your server's map folder right, or if you're using a collection with the maps in and it doesn't download them, make sure the collection is public and not friends-only / private.

[PeterChamp]

[QUOTE=Tenrys;44696868]Simply means the map is invalid or doesn't exist. Put it in your server's map folder right, or if you're using a collection with the maps in and it doesn't download them, make sure the collection is public and not friends-only / private.[/QUOTE]

I just copied the ph_kleiner.bsp file into my Gmod_server\garrysmod\maps folder and the same error still comes up. I also checked that the collection I am using is public and it still doesn't work. Any ideas?