You should be able to create and save a cookie exception. Two options:

(1) While you are on a page on the site, call up the Page Info dialog using one of these methods:

• Ctrl+i (for Mac, Command+i)
• (menu bar) Tools > Page Info
• click the lock icon in the address bar, on the drop-down click the > button, then at the bottom click "More Information"

When the dialog comes up, click the Permission icon at the top to show that panel.

Scroll down to "Set Cookies" and uncheck the "Use default" box, and then select Allow to let the site set persistent cookies. This will create an exception to clearing cookies at shutdown.

(2) On the Settings page, Privacy & Security panel, "Cookies and site data" section, click the "Manage Exceptions" button to open a dialog for creating a site "Allow" exception.

Please note: when you use the "Clear history when Firefox closes" feature, you should NOT turn on clearing of "Site settings" since that will remove your exceptions. You can scroll down to the "History" section, then set the selector to "Firefox will: Use custom settings for history", to gain access to the Settings for this feature.

This worked, thank you!