Nick here from Shopify.
It's very difficult to know why your store/ account might be on hold without any more information or a screenshot to see what you see.
Some of the primary reasons for this might be the following:
But it could also be a number of other things. We have a topic which goes into more detail on this that might be worth reading, FAQ: Why is my Store Unavailable.
Because we can't discuss account specific details in the Community right now, you might want to talk to someone in real time about this. If so, you can reach out to our support team directly if you'd like. You can visit our support team here and log in to your account to talk to someone in real time if you want to explore this further via this route.