No operational spares
If AJ could get more 717s, he would. They break down just like any other aircraft. If a DHC8, 737, Airbus, etc.. goes u/s, there might be one in a hangar or sitting around on an apron that can be used instead with minimal or no inconvenience to the travelling public.
Cobham are short of crews just like every other airline and every other airline are cancelling flights for one reason or another as well.