I have Roon Core on a Sonictransporter i7 cdr. It worked perfectly for about 2 weeks, until we were away for a week. When we returned, the i7 would not power on. I determined that the power supply had shorted - probably lemonade from my granddaughter. I bought an HDPLEX 300W, and the i7 powered on, but now the Roon controller app (on a Samsung S 21+) cannot find the Roon Core. I have tried replacing the ethernet cable (Audioquest Vodka, 5 m). I tried putting the cable in the router instead of the switch. I tried serving the core from a laptop connected via ethernet. No joy.
I have had a similar problem. I suggest replacing the micro SD card that contains the operating system for the SonicTransporter. You can get one from Small Green Computer. Price was $28 but may be a bit higher now.
Thanks much for your help. I was considering sending the Sonictransporter in to have an SSD installed, so your advice decides it - I’ll let someone who isn’t a peril with a tool to any luckless nearby do this.