I did some updates to the Debian packages but some final testing
revealed that the "Sync now" button in sync-ui is disabled. Syncing via
command line works fine.
The changes to the old packages are commit 8765654ff355aed3b982bd965e98c00dfd19d1c3
(libical: support libical v3) in libsynthesis and
(GNOME: replace gnome-keyring with libsecret) as well as
(libical: support libical v3) in syncevolution.
I have to admit that I don't use sync-ui myself but only check if it
works when preparing an update, so I can not tell when it really
stopped working. Due to the libical3 transition I can't really check if
this also happens with the old package. Any hints how I can debug this?