Mower stalls when I engage blades.

Hi. I have a John Deere zero turn mower. It runs great and cuts just fine. However, I just installed the power flow bagging system and now the mower stalls when I attempt to engage the blades. Initially, when I first installed the power flow unit, which is belt driven, it worked but the mower struggled to get the power flow going but it eventually did. Now, just a few days later, the mower can’t get the power flow going. It doesn’t sound like a safety switch issue as the engine doesn’t just cut off, rather, it struggles and it sounds like it wants to go but the engine stalls … any help would be much appreciated!