Hi

This does not sound like an issue with Firefox, but possibly something to do with the Yahoo fantasy football platform. Their support team should be able to help with this.

Are the sites linked together with a shared login?

Firefox's "Total Cookie Protection" feature limits how sites can use "third party" or "cross-site" cookies, meaning cookies from different websites than the one you see in the address bar. This protection limits cross-site tracking, but also cross-site verification that you are signed in.

You can make exceptions to this feature when needed (for each server that you visit as part of the process of using this company's services). Try clicking the shield icon at the left end of the address bar (next to the lock). On the drop-down, click the blue slider switch to disable protection. Repeat on the site's other servers as you encounter them.

More info in the following articles:

• Introducing Total Cookie Protection in Standard Mode
• Total Cookie Protection and website breakage FAQ

Any difference?