Cal Spa "Sn" display

My Cal Spa will not start (possibly following a close lighting strike) I get a "Sn" display reading but tub will not turn on. Any suggested diagnostics I can do?

[Mary]

You can try unplugging the spa sensor harness, wait a few moments and then plug back in. You would want to turn the power off before doing this. Usually a SN error code is signaling that one of the sensors is failing, but since you said that it was a possible lighting strike then your circuit board could have been damaged.