Could you tell me if this is a slam dunk case or not even worth bringing to court?

I can't tell you whether you have a "slam dunk", but there are issues here which could make a good claim or (depending on some facts which I don't know and which may be contested) coudl be a waste of time.  Some of the questions I would have are:           why didn't you receive any notification?  Was Shopify negligent or was the problem not of its doing, such as their notifications going into your junk folder or you chaning your email address without notifying them?;           does your contract with Shopify bar any claim for consequential damages (without getting into a long technical explanation, the damages you would be seeking are consequential damages)?  If so, and if the law that applies (might be California, might be where Shopify is, might be another jurisdiction specified in the contract) is like that of NY, that clause would be enforceable unless  you could show that Shopify was more than just negligent, but was at least reckless in failing to notify you;           why didn't you remember to renew your website?  Granted Shopify was supposed to notify you, but it wouldn't have been hard to note the date in your calendar;            who owns the intellectual property rights generated by your website under your contract with Shopify?  By using the trade name in commerce, you may have acquired common law trademark rights in it (I assume that you did not register the trademark), even if you no longer have the right to use the website.  If so, you would be able to prevent anybody else from using that name or a confusingly similar one in the same field of commerce.  Probably the Shopify contract precludes this, but you shoud check. It may be worth consulting with a California attorney, preferably one who is familiar with intellectual property law.