What worked for me (After several lost hours) was to delete the app from my iPhone (iOS 14.4.1) and delete all data.
Then when reinstalling the app it will ask you to allow network discovery, location services, etc. After this, I was able to pair a ZJSB9-80 WIFI device.
Hope it helps someone else!
It did work for me (iPhone 12 Pro, IOS 14.4.1, iPhone 7 iOS 14,4.1, iPhone SE 1st generation iOS 14.4.1. After meny meny lost hours):
Thats All Folks!!