Why do I have to reauthorize my Synology backup with Time Machine?

Episode 1508 (1:26:00)

Tim from Franklin, OH
Synology DiskStation DS216

Tim uses Time Machine for his backup, but the backup fails intermittently. His Synology NAS is citing improper credentials as the cause. Leo says that encryption certificates need to be renewed from time to time, and if he's encrypting his data on backup, that could be the issue.

There is a post on Synology forums about this: Time Machine, Making it Work. Learn from my Suffering. There are some steps that can help.