If you're getting logged out of Momentum each time you open a new Firefox browser window it is likely because your Firefox settings are set to automatically delete your cookies whenever you quit/restart Firefox.
To fix this, uncheck the Cookies section in your custom history settings.
- Type/enter: about:preferences#privacy in your address bar.
- In the History section, click on the dropdown next to Firefox will and select the Use custom settings for history option.
- Click on the Settings... button near the bottom right of the History section.
- Uncheck the box next to Cookies, then click OK.
If you're still having problems get in touch!