My Nitrokey Pro suddenly stopped working with Thunderbird 60.5.1. (under Linux Mint Cinnamon 19.1 with latest updates applied)
While in the past I was asked for my User Pins when I started Thunderbird, this does not happen any more. The Certificates are still registered (visible in Thunderbirds Security Tab),
but not accessible. Neither sending signed messages nor saving a draft is possible:
Unable to save your message as a draft.
Unable to sign message. Please check that the certificates specified in Mail & Newsgroups Account Settings for this mail account are valid and trusted for mail.
Starting the Nitrokey App also claims that Nitrokey Pro succesfully connected.