Try clearing cookies and cache by clicking on the Ctrl Shift and Delete keys on your computer
Restart your computer
If that does not help then try another browser like Firefox or Chrome
The other thing is to check to make sure the browser you are using is up to date
Google the browser updates to check
Hopefully something may work but it is trial and error
If it is the phone app then try using ebay through a browser and not the app
There are many problems with the app
