This is the message I get when I try to sync two of my five Boinc clients with bam.boincstats.com.

Of course, I have double checked that I'm using the correct URL - in fact, I'm just using the hard-coded URL for BAM in the Account Manager dialog within BOINC Manager.

The two clients in question are Linux servers running Ubuntu 18.04 and BOINC Manager 7.12.0. Weirdly I have a third server also running Ubuntu 18.04 and BOINC Manager 7.12.0 which will sync with no problem at all. No firewalls etc set up on any of the three servers.

The other two clients that sync just fine are both BOINC Manager 7.14.2 running on Win 10 and MacOS Mojave respectively.

I found a few threads in these forums where something similar was reporting when the boincstats.com's SSL certificate had expired, but that doesn't explain why some of my clients sync while others don't. (Surely none of them would sync if the problem was caused by an expired SSL cert.)

They both show up in my hosts list because they've been able to sync previously but it looks like the last time they did was 21 December.

I'm all out of ideas for diagnosing this - any suggestions why this might be happening?