I also can not see the render cloud to purchase anymore.... If Next Limit are winding their cloud services, they need to let us know as this would be a complete disaster for me. I have 20 hours or so left on my account, so no need for top up just yet fortunately. You should put in a support request and see if you get an answer.
Ranch render farm is now the only one I know of that serves Maxwell 5. That is a bit of a pain to use, or at least it was, as all references needed to be renamed to fit their specific format.
Mods: Is this intentional?