You must have been able to log in to ask this question. If you logged in to another account, as far as eBay is concerned that account will be associated with yours. Account associations don't normally cause login problems, but if you have accessed both accounts from the same connected device it may be worth clearing your browser cache or cookies, restarting the browser and trying again.
Otherwise, to contact eBay go to "Help & Contact" or "Contact us" at the top or bottom of almost every page. Response times may be slow, and during the pandemic is limited to callback or live chat.
