And I also just saw I have this error as well

Host_Error: CMapLoadHelper::Init, map maps/rp_rockford_v2b.bsp has wrong identifier

Please try the following:

Please try the following before posting:
-Unsubscribe to all rockford addons, delete them manually from garrysmod/garrysmod/addons, and resubscribe. Restart gmod once after you've launched it and the addons are unpacked
-Load into gm_flatgrass first, then load into rp_rockford
-If you're opted in to any betas for Garry's Mod opt out
-Disable all addons except Rockford and both content packs and restart gmod (if this solves it, find out what addon is the culpret and share it here)
-Verify local game cache
-Update video drivers
-Save your garrysmod/garrysmod/data folder, completely uninstall gmod and delete any remaining folders, and reinstall

I just tried all of that. Do you think you could upload the bsp file somewhere because I can't get it to work on my server

If you get a program called GMad Extractor, you can unpack the .gma in garrysmod/addons and get the bsp that way.

That's what I've been using. Legit been trying everything and nothing will work. I've tried a few other maps as well. A few have work but they're from garrysmods.org I'm not sure why those work and this one doesn't.

same thing is happening to me, cant find a fix anywhere

Hey, I might be a bit late, but:

I used a trick to extract only the .bsp file from the addon, and I actually got it: {mediafire link}
It's a mediafire link and contains the .bsp file, should work. Message me, if you want the link.