I am experiencing the same issue, with a Synology DS1618+.
Yesterday evening I have updated the Synology DSM Software to DSM 6.2.4-25556, did not try to connect to Roon since then. As I tried to connect now for the first time after the DSM update, this is not possible.
@Paul_Johnston, you state that you did not make recent changes - could it be that your Synology device automatically installed this DSM version most recently? If so, was the connection to Roon possible until before the DSM update?
@crieke May I kindly reach out to you as well?
Your GitHub page shows fix reauthorization issue · crieke/RoonServer_Synology_Installer_DSM6@48db4ee · GitHub - could it be that there is a connection? How exactly did this reauthorization issue occur? For existing Roon installations, is any action from user side required, such as to re-install Roon?
Thank you in advance for a short feedback - with the upcoming weekend and no Roon available, it would be amazing if this situation could quickly be resolved.
Update:
I have found the thread Fix for recurring authorization prompt and this seemed to describe the same behavior. I have now downloaded the latest installer for Synology (x64) via https://roononnas.org/builds/Synology/RoonServer_Synology_x86_64_2021-03-08.spk , but after reinstallation and also a restart of the Diskstation, the issue persists.