I shared my experience there too. I was able to make them pair; they just stopped working (could have been only battery working, but I didn't leave them on long term to see if reports for that were still coming in...).
Just to let anyone else with this problem know, Sengled support appear to have acknowledged to me that their contacts and sensors don't work well with Hubitat (but that their lights and outlets do). The Amazon page for these contacts do say they work with Hubitat, though, so it's a mistake on their page.
The smaller Sengled contacts do work with Hubitat pretty good in my experience, but I'm giving up on these ones.