IF PC coats but doesn’t stick after baking the first place I look is bullet contamination (usually quenching in contaminated water)
2nd, IF you don’t have a PID controlling your oven (if you have a convection oven you need a separate power circuit for your fan or the PID will burn it out) You need to test the temperature setting of the oven with a thermometer on the baking shelf EVERY TIME the surrounding temperature changes due to the location and type of thermometers they use on the countertop ovens.
I have a heat-sinc on the bottom of my ovens (material that holds heat to help the oven return to temperature faster after it has been opened) I use ceramic BBQ briquettes, you can use lava rock, fire brick ---
Baking I have tested many brands and colors of PC, researched their bake schedule, and have found the 25 minutes in my oven preheated to 400F/200C meets all requirements. For larger bullets or if you want a better finish go 30-35 minutes.
You can restore many older powders by drying them out in an oven <140°, in front of an AC.
Pre warming bullets (<150° if you can handle them without gloves their good, too hot you will just get a globby mess) also help stubborn PC stick better.
Then there are many powders that just won’t work without spraying; stick with gloss/high gloss polyester (TGIC) or polyurethane PC
Many fancier powders are meant to be used over a coating of another powder
Always remove all excess PC before baking
