katiemarie2013:
You wrote: "I only have one wifi ID".
So, does your WiFi not have two WiFi frequency bands (~2.5 GHz and 5 GHz)?
Or, have you set the WiFi IDs on both bands to be the same? (Supposedly that is the preferred configuration.)
You wrote: "I only have … one Apple ID."
So, you only have one Mac account, using the one Apple ID? The same Apple ID used on the "iPad Pro 11 inch 2018"?
I found that my problem was that when I had run a test, earlier, with my other Mac account, using a different Apple ID (which had successfully found the iPad with that same Apple ID), I had left that account open, in that state of having found that iPad!
So. My Mac mini was sort of "blocking" itself.
(I also found that the Mac mini "could not" connect to that other iPad because it wasn't set up for "two factor authentication." But that was expressed to me by an error dialogue box, which you haven't mentioned.)
Another thing that may have escaped your attention—because it had escaped mine, until just now (when going back to the other account, for further testing): The Mac will only "see" the iPad if the iPad is "awake"! (It may need to be unlocked [passcode, Touch ID, Face ID], as well.)