I had an issue with Google Authenticator earlier, whereby the generated code was rejected by my Synology DiskStation. It was all fully set up and worked fine, so was surprised when it failed. Fortunately, there is the option to fallback to email verification.
Having logged back into the DSM, I tried to reset the 2-step verification setup, but that too failed. I then noticed that the time is off compared to my iPhone, where Google Authenticator is running. My DSM was previously syncing against time.google.com. Switching it to time.nist.gov solved the issue.
Tags: google authenticator, synology ds