Do you find an answer. I get the exact same thing on a Intex PureSpa SB-H10. I've inspected water rotor, flow sensor and the 2 heat sensors. (going to check remove water heat sensors again one at a time to see what happens). I'm not giving up yet. However, I order a Coleman Spa from China in the meantime (4 weeks to get here).
Intex PureSpa, no beeps, no error code, shuts off, circulation and/or heat light turn off except power and just displays temperature. - PureCrap