no smoothie in loop

[scotheath]

Just finished a smoothie build, set trim pot and rocked it before I boxed it all worked good, (having said that I did all that into the front of the amp).  Quite happy because there is usually an issue for me at that point. installed the 4 screws holding the bottom of the box on and put it after my chorus pedal in the fx loop warmed up amp and... NOTHING ! WTF !. Removed smoothie from the loop and I got sound again. Tried again making sure all hooked up, and again nothing. Put it back in front of the amp and there it is, works like a charm. Not sure what to make of this. I've only built an OD (green Bean)and a couple distortion pedals(slow loris, and a mangler), which all work but all going into front of amp, not sure in a pedal what the difference would be. I'm completely stumped. anybody have any ideas

[scotheath]

Spent some time messing with placement of pedal. Turns out it works if its the only pedal in the loop. Same as into the front of the amp. only works if no other pedal in front of it or behind it.
Anybody ??