User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:70.0) Gecko/20100101 Firefox/70.0
Steps to reproduce:
Navigate to https://www.ebay.co.uk/, select "Sign In" at the top left of the page. Enter user credentials.
When credentials are entered (whether by built-in password manager or manually) the large "Sign In" button remains greyed-out and unselectable, leaving the user unable to login.
When credentials are entered (whether by built-in password manager or manually) the large "Sign In" button is blue and selectable allowing the user to login to the ebay site.
I have just received the update to Firefox 70.0. This website worked perfectly fine with Firefox versions prior to this.
I have tested the reported website working with Chromium 76.0, Tor Browser (based on Mozilla Firefox v.60.9.0esr and v.68.2.0esr), GNOME Web 3.32.2 (based on WebkitGTK) all which behave as expected. (Please see screenshot attachments).
I have of course tried disabling all plugins etc as a matter of course