Did this just start happening or has it always done this? If recent, did you update Duplicati or something else on your system since the last successful run?
Do you recall if you have usage reporting disabled?
If not, try disabling it via the environment variable setting then running Duplicati from that command line:
The certificate error makes me think this is a mono issue, but even so as part of the usage reporter it should probably be handled as a warning rather than an error. What do you think @kenkendk?