DO NOT run the pump until you're sure there's no ice in the system!!
First thing I would do is put an open-ended hose onto the solution outlet, to allow for expansion.
then I would fill it with water and heat it up to defrost the plumbing, let it sit for an hour, run the vacs to get a bit of extra heat in there and then run the pump. Make sure it's outside when you start the pump up otherwise you might have a small flood to deal with

p.s. freezing water obviously expands and it will find the weakest point in the system. This might be a hose connection, rather than the pump itself