Synology NAS Let's Encrypt Certificate error: "The Operation Failed"
Issue
Trying to add Let's Encrypt certificate on Synology DS918+. The process fails with error:
The operation failed. Please log in to DSM again and retry.
There are no obvious reasons for the error. Port 80 is open, Synology Log Center doesn't have any clues.
Read more: Synology NAS Let's Encrypt Certificate error: "The Operation Failed"