Some issues…
OEM forks are for sale to bike companies to fit to new bikes. They are not generally for sale to end users/or shpuld not be.
The probably means you are not the 1st owner of the fork (technically) so you may not have a warranty.
Your initial warranty will be with the e-bay seller (were they listed as new?) if you have only just got them you could raise a dispute for not as described.
Your best bet would be to initially go through the ebay seller, if you can’t get hold of them at all then that is poor form especially if they are still trading on ebay.
You can try Mojo but it will be at their discretion (the forks may be non UK or anything) they might be interested to know who is flogging OEM as new too.