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Hi whats the make and model of the spa?
Has this fault only recently occured in terms of the flashing icon and the pump not starting when its being heated?
When the pump light flashes is their any water circulation or are you just referring to the jets not working?
In terms of the motor not starting \ only humming this sounds like its seized every now and again, its worth checking any filters are free from debrit and there arent any air locks.
If all this comes up empty then its time to service the motor and give it a good greece, check the impeller and motor brushes, which is about 20 minutes work.