Why can't I register my domain despite successful monthly subscription?

I can’t register my domain. I thought I could register somewhere else and come back here and put it. But I got devastated, not that I’ll wait after 60 days before I can transfer but I can’t still purchase again from my Shopify app/site. But my monthly subscription went through. Don’t know why my domain own can’t be through. I don’t know if there is any solution. I have tried other solutions. Still yet.