I can't help because I've shut my ST Hub and deleted it from my account. I used the IDE to add (and Publish) both the SmartApp and. the DTH, but that's as far as I get.
In the SmartThings (iphone/ipad) app, there's no option to install the SmartApp. I turned on Developer mode but there's still no + in the Automations tab.
I deleted the app and re-installed on my Iphone IOS15. Under automation I clicked the + at top of page and then select add routine. When I scrolled down I found all my groovy apps that are currently in the IDE and I was able to re-install Hubconnect.
That's my difficulty... there is no + on my Automation page. Favorites, devices and Life all have a + but Automation: nada.
YES!! it does. There at the bottom is the HubConnect smart App for me.
Lemme see if I can config it. Been so long, I'm liable to make every error possible.
It was more clicking than I remember but I got a HubConnect Remote for SmartThings (Hubless) again. 
I have no devices on ST, of course, so I'll use the IDE to create a "Simulated Dimmer" and mirror it to Hubitat.
That went well...
And sure enough, it appears on Hubitat "instantly".
Control works as it should... I set the dimmer on ST's device to 29% and...
On Hubitat:
This is obviously not ultra exhaustive, but it's enough to say that a message of
"We're having trouble connecting. Check your network connection and try again."
isn't an inherent problem with either ST's infrastructure or Hubitat's.
did you lose all your devices and settings by doing this?
I lost all the setups in Hubconnect if that is what you mean.
yes, that is what I mean and exactly what I am trying to avoid if at all possible
Download the Hubitat app
