Homie Vehicle Delivery Constant Busy Signal

Okay, I remember this happening with the OG version of SRTT, but that was years ago, and I have no recollection of how I was able to resolve it.

Long story short, it was working just fine, then all of a sudden, all I get when I try to call for a vehicle is a busy signal. I am not in the middle of any mission when I try. I am in SP and not in co-op. Also, I tried reloading the save, and additionally I exited the game to Windows, and restarted it, but it still doesn't work.

Any idea how to get rid of this?