Two adapters, two iPad minis (I believe in spares)
I have the same problem as you. Just initial fiddling a few minutes ago, I got the spare iPad to connect to the spare adapter. The only thing I did was remove and redownload the program from the Apple App Store. Since this program/app has been working flawlessly for over a year, I know have to "relearn" all the ins an outs, like custom dashes, sending and receiving custom dashes, all the settings, etc. Downloading the new version of the app seemed cause the problem, deleting and reloading the app "seems" to have fixed the problem, but I am now back to square one.

Sorry for the babbling, will calm down and take a look tomorrow and try to figure out what is going on. Very frustrating to try to work with a Windows programmer and a Windows program on an Apple, but it is a GREAT PROGRAM, but hard for this old man to figure out, very labor intensive and Mark's support is also a little confusing.

I, too, have now got my spare adapter to talk to the backup iPad. I figured mine out at about 3:00AM this morning, so couldn't start the motorhome to fully check it out. I will do that a little later this morning, when kids are screaming and dogs are barking and will then address the primary iPad "nailed" to the dash.

I was still a little confused about where the custom dashes were being stored, both on my iPad and where in the BlueFire app. Think I got that figured out now. This was NOT the fault of the App nor the iPad, just ignorance on my part. But, again, I think I now have a handle on that (for now).

To be fair to Mark, the whole problem of losing comm with the adapter may not have been just the update to his App, but a combination of that update and my iPad update to iPadOS 15.6.1. AND the fact that I haven't really used the program since May.

Either way, there is a work around, so all is right with my world for now. I have been using BlueFire for over a year with no problems, that's why I was so frustrated when this problem came along. I'm spoiled by Apple and MAC stuff and always start kicking and screaming when forced back into the "PC World" and it's vagaries.
I'm thankful for Mark doing all the heavy lifting to make a DOS/Windows app do it's magic on iPads, etc.

Mark has got the best program out there for designing and making my own instrument board. It is not his fault that I don't stay on top of the App because it has proven to be pretty solid and invisible, maintenance-wise.

WazMO

AH, the 4.1 adapter, I assume, I am going to get in touch as both my adapters are 3.somethings, and I think he has a special about upgrading the firmware and getting the 4.1 hardware at the same time.