It sounds as if you have set up two step verification.
If you don't want that security measure follow the instructions on the link below.
It tells you how to set up and remove two step verification.
https://www.ebay.co.uk/help/account/protecting-account/tips-keeping-ebay-account-secure?id=4872&st=3...
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
