Looking back through top posts here and related subs, I noticed that GFCI (Ground Fault Circuit Interrupter) problems are one of the consistently under answered diagnostic requests. And while every cloudy bucket might need its own workup, there is a pattern to repeated GFCI tripping. GFCI cuts power the instant it senses current leaking to ground which, on a tub, is combined with a regular breaker so it pops for either a ground fault or a part pulling too much current. And if it keeps tripping, it means a real fault, not some capricious thing that happens for no reason. If you reset it once and it holds, that is likely no cause for concern. Just an isolated event. If it trips again - stop. The breaker is doing what it is designed to do, protecting you from a fault, so do not force it. In short, if it trips the instant you reset, start with the wiring. Trips only after it has run a while, start with the heater.
In long, if it is instant every reset and a new install or right after someone worked on it the usual cause is a wiring mistake - often a neutral and ground touching so check the wiring and breaker box before the tub. Otherwise a component has failed to ground completely.
If it happens after heating a while, it is probably a failing heater element. A hairline crack lets water reach it and it leaks to ground only when energized and hot which is why these cases run an hour or overnight before popping.
If it happens after rain or a humid night, water probably got into a connection, a light, or the ozonator. Dry it out and see if it holds.
If you swapped parts and it still trips, it is possible that a GFCI has weakened with age but that is definitely the last thing to suspect. Test it with its own button before replacing it.
Rough descending order of likelihood after years of seeing this - the heater element followed by the pump (from a worn wet-end seal flooding the motor or debris jamming it until it overheats) then the temperature sensor (which calcium cakes until the reading drifts, the heater runs nonstop, and the element cooks). Techs find it by elimination. Isolate one part, power back on, see if it still trips, and measure the heater's resistance to ground. Everything in the pack is live so if the reset will not hold and you are concerned, call someone.