If you cancelled the return you cannot open another for the same item.
However, it is worth asking Customer Service and explaining the mistake, see if they will open another return case, they are not obliged to, but as said, worth a shot.
This is the easiest and quickest way to contact eBay Customer Services, for a Call Back option.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
Lines open 8 a.m. - 10 p.m. on weekdays
9 a.m. - 6 p.m. on weekends.
Automated agents will be available on chat outside of the above hours.
I recommend contacting CS first thing in the morning as there's more chance of Dublin answering.
@bluebelldeborah