Firefox won't open links from Thunderbird email program

In the last week, all of a sudden Firefox won't open links inside Sandboxie when I click on them from the Thunderbird email client (also in Sandboxie). Nothing happens when I try and Firefox doesn't react in any visible way. This still works when I make my default browser Chrome and run Thunderbird and Chrome inside Sandboxie. It also works when I run Thunderbird and Firefox outside of Sandboxie.


Sandboxie 5.31.6

Firefox 70.0.1

Thunderbird 68.2.1

OS Windows 7 Pro 64-bit


Unfortunately Thunderbird, Firefox, and Sandboxie have all had updates in the last week or so and I have been unable to track down specifically what might have changed. I haven't done anything to change my Sandboxie configuration. Is Sandboxie somehow blocking the communication between Thunderbird and Firefox. I have no problem copying the link in Thunderbird and pasting it into Firefox inside Sandboxie.