Firefox may be preventing you from viewing the promotions page based on the Privacy Protections settings you have enabled. To resolve the issue, you can follow the steps here:
- Choose the Menu (3 stacked lines) button in the top right corner of Firefox.
- Choose Privacy Protections from the Menu.
- At the top of the page, in the Enhanced Tracking Protection box, select Protection Level is set to Strict.
- On the next page, choose Standard.
- Choose Reload All Tabs button.
After those the 5 steps, you should be able to view the Promotions page without further issue.