Typically that challenge occurs when the browser has no cookie saved from a previous eBay session, or when using a different IP-address.
Have you changed anything about your setup lately? New browser, or new privacy settings or software? Using a VPN or hotspot?
Make absolutely sure you are using the correct password. Using the wrong password will cause you to keep getting challenged (though that is not the only reason for such challenges).
Try another browser altogether or a private or incognito browser window.
Preferably the latest version of a browser you have not used before, with default settings and no add-ons installed.
Or try signing in using the eBay app.
Try using a different link to sign in, particularly if you are using an old bookmark to sign in.
Since you seem to be signed in to your account in the community pages, try using the link to your My eBay page located under your icon in the upper right corner of the community pages.
In some cases you may be able to avoid a Captcha loop by signing in using a social media account if you have previously linked a Google, Apple or Facebook account to your eBay account. If you can sign in using the app, you can use that to link a social media account to your eBay account.
If you are able to sign in using the eBay app, you may be able to break the sign in loop by changing your password using the app. Then sign in using the new password on your desktop.
