Whenever my wiim of choice don't show up in Tidal, or only shows as chromecast, I find that restarting Tidal usually works.
Sometimes I find I need to restart my tablet instead.
But I rarely need to restart my wiim.
Sort of similar thing happened to me last night (and has happened once before too) - I opened the wiim app and it started searching for my devices instead of just showing them immediately like it normally does. A short while later it showed them all as being on a different network; effectively unusable.
I closed the wiim app and reopened it, this time the mini, on wifi, was available, but the 3 pros, all on ethernet, were still, apparently, on a different network.
I ignored it, went to do something else, and when I came back the screen showed them all available as normal again.
So, no real solution for you, just that sometimes restarts of various things seems to be required!