When I had to deal with proline on my BK mini 200 they were helpful for the most part, They did get me a new impeller free of charge but it did take them 2 weeks to get it to me. Thankfully Daniel from Wai's lent me one of his skimmers.

They did admit to me that there is an issue with some of the impellers on the Bubble kings. If you have the impeller out of the pump and you hold the impeller the magnet is supposed to be fixed to the shaft. If the magnet spins on the shaft it can cause the pump to slip on startup and not operate.

just something to try. with the volute casing off, If the motor is trying to start and the impeller is not spinning it most likely is the impeller or impeller bearing, if the motor does not even try to start then the pump is dead.