So just FYI, if you are impatient you can change the channel to anything other than 20 and the warning will go away. It is specifically an issue with 20, but only in some cases and does not affect everyone, hence why if its working fine the normal advice is to dismiss it. If you were having the issue you would know, zigbee would be awful. If you switch I recommend 25 because it is least likely to have Wifi interferences since it overlaps only slightly on one side. Sometimes a channel change will cause a few devices to drop off and not find it again, so you may have to pair some devices again.
OR if you just wait a little bit I am sure they will fix the alert so it can be dismissed.