Same account that I always use. I never downgraded the viewer since updating it to 6.10.8. I know the issue is on the RU server side because my laptop with a previous version of the view had the same issue.
Something during the RU Server upgraded modified my address book.
We have just managed to reproduce the issue and confirmed that it's a bug on the server. This is how you can reproduce it: add a new connection to your synced address book in Viewer and then edit it, e.g. change its name. The connection will disappear from the Viewer book but will remain in the server book.
We will be fixing this bug and updating the server later today. The server version will be incremented too for you to be able to distinguish it from the current one.
Sorry for any inconvenience.
P.S. Viewer 6.10.8 and Host 6.10.8 are not affected by this bug, it's only the server that needs fixing.
The new Server version 126.96.36.199 is available for download. If you are updating from 188.8.131.52 you may still need to restore permissions in your server book. If you have a simple permissions structure, i.e. one account that has full access to the entire book, just do the following:
1. Update to 184.108.40.206 "as is", i.e. just run the installer and complete the installation.
2. In the server address book manager expand Address Books, right click on your address book and select Edit address book.
2. Click Security.
3. In the security window enable Replace all child object permission entires with inheritable permission entries.... This will grant the account (principal) in the list permissions to all objects in this address book and restore permissions for the entries where they were deleted due to the bug. Therefore, when you sign in on the Viewer your "lost" entries should re-appear in Viewer address book.
If you have more granular access levels, i.e. other accounts with access to only some folders you will need to do the same procedure but on the respective folder level.