Mark V 35 effects loop issue?

[nremondelli]

So I'm trying to run my EHX Memory Boybpedal in the loop. Send-->input, output-->return. When I turn the amp on the volumes is barely audible. When I unplug the cables from the loop the volume returns to normal. Running the ordeal in the front works fine. Issue?

 

[Monstercastle]

Maybe the pedal can't handle a line level signal.