i just got a used sundance sentry 800 and the low circulation pump wont start but the high will is there a motor problem or a relay problem? it just shows the FLO code?

Likely to be a prob with the 2spd pump - 2spd pumps are notoriously unreliable compared to single speed ones.

I'd use a meter to if power is going to the low speed circuit on the pump. If it is getting power, you may need to replace the pump.