I haven't used my pool heat pump in a few months and when I recently turned
it on I am getting a Low H2O error message and it is not starting up.
Usually that message is displayed when the pool pump is off but now I see it
when the pool pump is on as well.

Does anyone know what might be causing this? The pressure on the pool pump
hasn't changed from where it always is. Thanks in advance!

Dutch Buckhead writes:

Is that switch something that is fairly easy to replace?

It can be. Not familiar with your particular unit. Sometimes its a
separate piece of plastic plumbing that has to be cut out of the
circulation line and replaced.