Hank here from Shopify!
There can be a few reasons as to why that error message appeared, but can you share your store URL and I can take a look at this on my end to see what the issue might be?
Normally this appears for stores still in their trial period as the checkout is disabled until a paid plan is chosen. Or it can appear if there has been a change to the theme code of your store.
And also there are times that the browser is specifically at fault, which may be the case for you here as you mentioned it worked in Chrome.
Let me know how you get on with this!
All the best,