Re: why won't firefox let me remember usernames and passwords?
Please follow the below steps it'll help you resolve the issue
1) At the top of the Firefox window, click on the Firefox button and then select Options .
2) Select the Security panel.
3) If it isn't already check marked, check Remember passwords for sites.
4) To the right of Remember passwords for sites, click the Exceptions… button .
5) Make sure that the site you're trying to log in to isn't in the list.
6) If it is, select the entry and click Remove.
7) Click Close.(If none of the entry found in Exception then too please click on Close)
8) Click OK to close the Options window .
Thanks, Please let me know if the issue still persist