Hey Andrew,
posting issues in this community is fine. 
But sometimes, raising a ticket instead is better. It could also be that raising a ticket after you posted here can be the next steps. It all depends on the issue and what info it involves to be solved. I do like when users post issues here, because this is helpful for other users as well - as you never know who might have a similar issue and can see possible solutions. That is, what these communities are for, right? 
Anyway, about the relationship: Your first contact should always be your provider unless you have the Sitejet Studio version (Studio is the standalone version under sitejet.io ) They would then get in touch with cPanel support for troubleshooting.
We do also support but ours is limited to issues inside or from the Sitejet Builder. Since most users do not know where and how an issue is happening, it is of course not possible to know where to post. That is why under some posts here or via tickets to us, you might get a response as “Please contact your provider or cPanel directly” - which basically means it is something they have to fix probably.
But, it is totally okay if you feel like posting everything here. I am here to guide you to the right direction.
Hope this helps clarifying it a bit.
Regarding your issue: In this case, you need to really contact your provider so they get in touch with cPanel. It seems that there is a server issue - if we have to provide assistance, cPanel will come to us.