Can you provide steps to replicate your issue?

Are you possibly located in the EU because that can cause websites to display a confirmation asking to accept cookies ?

The status of this confirmation is likely stored in a cookie, so you need to keep cookies for these domains to prevent getting this dialog each time you visit this website. If you do not keep cookies and you use "Delete cookies and site data when Firefox is closed" then you will have to create a cookie allow exception.

• Options/Preferences -> Privacy & Security
  Cookies and Site Data: Exceptions

If you block all cookies then you may have to allow at least first party cookies for the current domain.