Both the iMac and Synology are connected via Ethernet to a devolo dLAN 650 triple+ powerline adapter. Pings work fine from the iMac to the Synology:
seanslattery@iMac ~ % ping 10.7.151.3
PING 10.7.151.3 (10.7.151.3): 56 data bytes
64 bytes from 10.7.151.3: icmp_seq=0 ttl=64 time=0.373 ms
64 bytes from 10.7.151.3: icmp_seq=1 ttl=64 time=0.330 ms
64 bytes from 10.7.151.3: icmp_seq=2 ttl=64 time=0.385 ms
iMac 27inch 2019, MacOS 10.15.5, Ethernet connection to Synology
Description of Issue
Roon client on iMac failing to connect successfully to the Roon core. When I start Roon client on the iMac it shows the “Choose your Roon Core” window with my Synology machine as an option to connect to. The status for Roon on the Synology is shown as Ready with a green circle. The core is described as "Linux 4.4.59+/10.x.x.x, Version 1.8 (build 790) stable.
I click Connect beside this Roon Core (the only one displayed) and I get the message “You’re already signed in” and it tells me I’ve already setup another core and offering me the chance to Unauthorise my Roon core on the Synology.
Many thanks to you both! It’s counter-intuitive, but Unauthorize unblocked the server (and looks like it didn’t actually unauthorize it).
That didn’t completely fix things for me - Roon clients could connect to the server, browse music etc. However no audio devices were available and it was impossible to add one. This was only fixed once I stopped the Roon server package on Synology and restarted it. Now everything appears to be working.