The "email already in use" message means that email address is linked to another eBay account. Use a different email address. Each eBay account must have a unique email address.
I do not think that everyone is having the same problem in that you are.
There may be something about your current setup that is causing problems for you. Try something different.
Try a different browser (or a private or incognito browser window) to sign in to rule out a browser issue.
Try a different link to rule out a bad link or an improper redirect.
Try a different device to rule out a device issue.
Try a different network to rule out a network issue.
Try signing in to ebay.ca instead of ebay.com to see if that works differently.
If you have previously linked a social media account to your eBay account, try signing in using your social media account.
Try signing in using the eBay app. If you can get in via the app you can use that to change your email address, change your password or to link a social media account. Then go back to your desktop and try again.
