refer to

• Websites say cookies are blocked - Unblock them

article

Also:

• Check any privacy-related add-ons in case they are blocking Google cookies

• In case your Google cookies are corrupted, try removing them. Save any work in progress, then, while viewing a page on the site, either:

- right-click and choose View Page Info > Security > "View Cookies"
- Alt+t (open the classic Tools menu) > Page Info > Security > "View Cookies"

In the dialog that opens, you can remove your Google cookies individually. Then try reloading the page. Does that help?

Clear the cache and the cookies from websites that cause problems.

"Clear the Cache":

• Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now"

"Remove Cookies" from sites causing problems:

• Firefox/Tools > Options > Privacy > Cookies: "Show Cookies"

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes