What happens when you try to sign in? How far do you get, and what stops you?
You are able to sign in to the community pages, or at least you are already signed in here.
Are you able to go to your icon in the upper right, click on that and open your My eBay page in another browser tab?
Try another sign-in link, particularly if you are using an old bookmark, to rule out a bad link.
Try another browser to rule out browser issues.
Try another device to rule out device issues.
Try another network connection to rule out a network issue. If you have the eBay app on your phone, try that when not connected to your usual WiFi.
If you have more than one eBay account, try signing in to another account (possibly in a private or incognito browser window) to see if the problem is account-related.
If you have a social media account linked to your eBay account, try signing in using Facebook, Google or Apple.
