ARC not playing

Roon Core Machine

SGC SonicTransporter i5

Networking Gear & Setup Details

HOT (my TV/ISP provider) Fiberbox mini, wireline connection

Connected Audio Devices

Number of Tracks in Library

Description of Issue

ROON 2.0 functions OK via WiFi/LAN
ROON ARC connects to the ROON Core, but when I try to play a track it says
“Can’t connect to Roon Core, check your Roon core and try again”.