I run Firefox standard (84.0.2) on my windows laptop (v10) and try to synchronize with my Mac desktop - OS X Version 10.11.6 with Firefox esr version 78.6.1. It worked in the past and I am not sure when the synch stopped. I have tried to look at the log in about:sync-log but am at loss to understand what all the code means. It does contain a lot of DEBUG ... Thanks for any suggestions!