JFC, I'm also playing with a loop because I want to use a compressor before a physical dirt pedal and just made a huge fucking mess in my newly cleaned studio changing out cables and getting pissed off that it wasn't working. Tried both In/Out 3 and 4, used my Loop blocks I had saved just for this purpose, kept getting silence. Go through all the internal settings in case I did something stupid at one point, nope....
After 75 minutes of fucking with shit, I realize the Out on the face of the AxeFX is turned down.