Welcome to the Spa Doctor.

Nothing comes on but there is power to the spa.

There is a sequence of events that occur when you power up the spa. First there is a CLICK. That relay tells you that power is being applied to the pcboard. If you don't hear this CLICK, then either power isn't being applied OR proper power (missing one leg of the 220vac) OR control box fuses are blown. The only way to properly to check is with a volt/ohm meter. If you know how, do so. Otherwise you need to have an electrician confirm proper power is being applied.

If you have confirmed that proper power is being applied and the fuses are OK and you don't get a CLICK, the problem is either the pcboard or the transformer on models that have separate pcboards. Since Jacuzzi began using transformers I have only replaced one or two transformers. So the problem is likely the pcboard. On some models the transformer and pcboard are included on the board so it eliminates the worry of buying the wrong part.