I have just recently set up a Roon Core on an iMac 2019 and have found connecting remotely from an iPhone X with the controller is hit and miss. The iMac is connected via WI-FI in a separate room to my router and is set up to sleep after 10 minutes. Not sure why sometimes it will connect and other times keeps searching for the core. This also happens with my MacBook. So what is the best practice apart from setting the iMac to never sleep if that is possible.
Post in support not here.
Same issue with mac mini - no connection during sleep. But, it is headless, so not a big deal for me.
I think there is a wake for network access option in preferences, but I could never get it to wake for screen share or Roon.
Interestingly I had to reset my TalkTalk router last week and since then the remotes have connected with no problem. Perhaps that may the solution i.e, do a regular reset of your router. The only problem with that is when the engineer set up the router and modem he told me to avoid turning them off to often as it may slow the speed down. But that’s another story. Modern technology eh .