There's been issues with HTTPS certificates recently - some important ones expired and a software update is required for the Lametric Time to fix it. Lametric support tell me that they're aware of the problem and are working on a fix.
Please make sure you have updated your LaMetric firmware to 2.2.2 version. It contains a fix for the issue where some apps could not fetch any data due to the new Let's Encrypt's intermediate certificate.
I'm currently running on 2.2.2 but have again issues with HTTPS certificates
I confirm (1 year later), that I still have the issue :)
... and my lametric firmware is 2.3.3