I checked the system issue post for the api problem yet it seems I stilll can’t do anything. Clicked to check availability multiple times, no fixes.
Same problem bro 
What to do now
It looks like the reseller API are down again. Currently all requests asking for if a domain is valid will return an error, thus preventing you from creating any new domain.
Please allow a few hours then retry.
All should be working again. As the system may go down again, please direct your attention to the pinned topic.
Thanks