Roon connectivity

I've been running Roon core 24/7 downstairs on a Mac Mini that sent files via ethernet to an Ayre QX-5 Twenty, a Roon ready device, and Roon bridge upstairs on an iMac that sent files via USB to an Ayre DX-5 DSD.  

I moved the QX-5 Twenty upstairs where Roon bridge successfully sends files to it via ethernet. I installed an Ayre Codex downstairs to receive files from Roon core via USB, but Roon doesn't reliably find the Ayre USB zone. At one point Roon offered Ayre USB and played the files sent to the Codex, but stopped suddenly and isn't showing the USB zone. Is there an obvious fix?  Same thing happened this morning.  Both the Mini and Codex are running 24/7.
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