Your spa doesn’t heat up or not enough.
Poor water circulation in the filtration pump.
Check that the water line in the pool is between the min and max limits. If this is not the case, fill or empty your spa so that the water line is between these two limits
It is also necessary to clean the 2 nozzles (suction and discharge) located inside the basin (photos). To do this, just unscrew these nozzles and remove any filth (hair, fur, dead skin...).
The problem can come from the filter cartridge. Operate the spa by removing this filter for 24 hours. If this works, then it is necessary to clean or replace the filter cartridge.
If, despite the tests carried out and the replacement of the filter cartridge, the problem persists, you have to replace the motor unit.