Does not play well with pedals?

I've had my GM36 for about a year and a half now, only amp owned previously was an OrangeCR120.
After being blown away by this amp I sold my orange and all pedals I had with it for the GM36.
Recently I've been getting back into pedal collecting only to be disappointed the sound vastly different than when I tested them out at the store. They sound terrible through the amp, whether it be in front of the amp or through the FX loop.
Does this amp just not play well with pedals at all?

It may be that you are using it in an incompatible way.  The amp has built into it an input buffer which acts like an overdrive pedal in itself if the input is high enough or if you engage the Boost.  Have a try lowering the input signal level out of your pedals and making sure your Boost is Off.