When you have a problem with one particular site, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

1. Clear Firefox's Cache

Tools > Options > Advanced > Network > Offline Storage (Cache): "Clear Now"

On MacOS, that may be under Firefox > Preferences instead of Tools > Options

2. If needed, delete the site's cookies here:

right-click the page, choose View Page Info > Security > "View Cookies"

Does that help?

I will try right now to see if it helps. did not work - where my names(s) would normally appear in the edit box there is only a blank space. If my names are being used, whose using them? My games profile shows nothing also. Any further solutions?

did you get my reply? if not will repeat it - I tried - did not work. There are no names in the edit box - and I used to sign in as grammapearl1 - now I have to sign in as merlthepearl - not my original name, just one of about 3 I used to play games. When I try to re-register, I get message that name is already being used. Could it be because I have played on using Safari?

If you can log in and play successfully with one name, that is good news.

Regarding the other names, you can't re-register them, but you might be able to recover/change your password. Often if your login fails, you can have a site email you a link to change your password.

If you have Firefox set to save your passwords, you might want to clear them for that site or perhaps all Yahoo sites. Check out the section of this article on "Viewing and deleting passwords": Remembering passwords | How to | Firefox Help.

I can log in but cannot play