There’s always two sides to a story, and while I know it can be easy to jump to conclusions given the way things appear sometimes, if there’s one thing I’ve learned in the rollercoaster of the past year, it’s to give folks the benefit of the doubt whenever possible. Especially when, in all fairness to both people, we are only hearing half the story.
Yes, $500 is indeed a good chunk of money, and it should have been returned to OP in a timely fashion, no doubt - but why jump to the level of suggesting rumors of financial issues, etc.? Poor communication, I can definitely see a point for given OP’s stated narrative, but other than that… it’s pretty easy to be an armchair warrior these days, isn’t it. 
OP, if you’re indeed having 0 communication from the broker in question, your likely best recourse is to work with your bank for Zelle chargeback support, and to make a post on their actual reviews thread, making it more transparent and giving them a chance to remedy the situation and respond as well.
Not sure we need to beat the dead horse further in this thread.