Just to check did you get an update for Roon when you got back, as there was one or two, depending if you are on EA. Have a look at Roon uptime just to check
As much as I like the improvements with ARC in the last two months, I have yet to have a trip outside of the country where it has worked for more than a day or so without having to go into offline mode.
Well, I am totally guessing here, but if your home network was not dual-stack (i.e., running IPv4 and IPv6 in parallel) and you were only running IPv4, that might work in your home geography but not in the geography in which you were traveling.
I did initially think that, but a lot of carriers use IPV6 for mobile phones these days, but they also provide IPv4 gateway’s which should stop this from failing.
Maybe there is not enough bandwidth for this or Roon is failing for another reason, but I am not sure what.
I had 4 foreign holidays last year and I think 1 day was the most that ARC worked for. I have convinced myself that it will be better this year, but I am also keeping PlexAmp and a large ARC offline download library .
It depends upon the peering arrangements between you and home. You are best off having IPv6 enabled on your home network. Modern OSs are actually tested presuming that it is enabled.