I have had Avast secure Browser installed for years and it has worked perfectly. For a few weeks now the links in emails arriving in Mozilla Thunderbird (update 2/7/20, 68.10.0 (20200629235513)) are not opening in Avast Secure Browser (83.0.4530.98) automatically. Instead an error message pops up to say "this file does not have a program associated with it." The Avast secure browser is set as as my default program.
Copying the link manually and pasting it into the Avast browser opens the correct web page.
If I change my default browser to Chrome, the links from the emails work. Changing it back to Avast Browser recreates the problem.
Is there an incompatibility with the Avast Browser which started in the last few weeks?
Starting Thunderbird in safe mode (without add ons) does not rectify the problem.
Any suggestions how I could get the link to the Avast program working again?