You don't mention the seller's location and that's kind of important information.
I'm going to guess that the seller is based out of Mainland China, or at the the very least, the item's being shipped out of the People's Republic. I suspect there's a lot of news about COVID in China that's simply not getting out there. COVID is likely still complicating things there to a significant degree. Then there's also the Meng Wanzhou thing, which has strained relations between China and Canada.
I'm not clear about whether your seller has sent a formal cancellation request through eBay or has merely messaged you that you should initiate a cancellation. If they've done the former, then accept their offer to cancel. If it's the latter, if you don't have a history of cancelling your purchases you should be able to do so with no harm to your account. Ideally, you shouldn't have to do this, but I think this is the simplest, minimal hassle way to deal with the situation.
Then look for your suitcase cover from another seller.
