What pump do you have on your SM250? Is it an RD3 or the AC Red Dragon 1?
Does the controller have the quick connect plug that allows you to unplug the motor from the controller?
What is the issue you are having? It likely just needs a deep cleaning. Take it apart and soak the motor, impeller and pump cover in un-diluted household distilled white vinegar for 10 minutes. Do NOT dilute it and do NOT soak for more or less then 10 minutes. Then scrub inside the blocks magnet cavity with a tooth brush. Use a dish brush to scrub the impeller, pump cover and outside of the motor. Then rinse well. The pump should look like new inside and out. Then reassemble. Do this even if the motor looks clean and even if you cleaned it with some other method. This is the best way to clean the pump and the only guaranteed way to clean inside the bearings. It’s not what you can see but often what you can’t see that will cause the motor to go into protection mode and fail to start. Do that first before jumping the gun. And if there is still an issue, the only thing you will likely need is a controller but we can cross that bridge after you do a proper cleaning and or after you let me know what the issue is.