eBay have just added more sections that need ean numbers. My products lie in these sections. I'd check your listings just to make sure.
Probably should have been more detailed in my message.
I know these are a thing now, my products were flagged as needing them or my listings will be ended. But when I go to apply the number there is an option for "does not apply" which i my case is all I need. I didn't know you could purchase product identifiers?
I'll try the does not apply tomorrow. Hopefully that fixes the issue.
I am not entirely sure it's as easy as just buying the ean and attaching to a product yourself. I've emailed some ean provider on eBay with some questions. I'll report back with my findings.