Do you get the button when creating a new listing from scratch, and did you recently unsubscribe from a store package, and were your current listings created while the store was active?
This might explain why you still have a store door, but its says the store doesn't exist when attempting to click it - this might also explain the lack of submit listing button when choosing sell similar, because any listings created with a store sub will have slightly different T&Cs than new listings after no longer subscribed, meaning they can't carry over to a copy of that listing. (eg listings created while subscribed to a store will maintain the store's FVF on sales until the next listing duration, after which the non-store fees will apply, so maybe eBay won't allow listings to be copied until then).
If that's not the issue, try a hard refresh on the listing screen (CTRL + F5) buttons rely on script and this will force your browser to re-download the page rather than pull from a saved version, if that doesn't work, try clearing cookies / cache and restarting the browser. If still no joy, try a different browser.
