It is not a scam if the message came through ebay messages
If you want to sell on ebay then you have to have managed payments
Ebay take the payment and once they have take fees off they put the remainder in your bank
It is not instant like paypal and can take several days
See the link
If you dont comply then you cant sell
Your buyers will still have the option to pay by paypal
https://www.ebay.co.uk/help/selling/getting-paid/introducing-managed-payments-ebay?id=4795
