Spa Heater Help

Newbie here. Could use some guidance.
About a year ago, we moved into a house with a saltwater pool and a 500 ga. saltwater spa. The spa has a Raypak Electric Heater (11kw). About a week after turning it on, the copper heating element broke (cracked in several places). I replaced the element and got it working for about a month before the same thing happened. In both instances, the pH was above 8 for extended periods before the failure.
Now that I have the water balanced, I'm ready to get the thing running again. Problem is, it doesn't turn on when I flip the switch. I checked and there is power coming into the unit. Any thoughts on what might be the problem? Also, is it safe to assume that the pH caused the failure of the 2 elements? Wondering if the copper and salt were the bigger contributing factor.
Thanks!

Chemical problems can erode heater elements, but splits in heater elements (at least, in water heater elements) result from dry-firing.

For this to happen on your spa, something is wrong not only with your circulation, but also with your controls: the heater should not be able to fire when there is air in the heater line.