You're on quite old versions of both Hubitat firmware and Blue firmware, so that will make effective troubleshooting difficult.
If the offline issue persists and you are interested in updating the Blues, perhaps this info may be helpful...
The Inovelli Blue firmware files and driver files are all maintained by Inovelli (not Hubitat).
The latest Blue driver is the 2024-05-30 version, and I believe the latest available firmware is v2.18. I admittedly haven't checked for a firmware update lately, but I lurk regularly in the Inovelli community and I haven't seen any references to a newer f/w.
The Blue driver is available via Hubitat Package Manager or for manual install, this link.
Alternatively, a (community-developed) simplified version of the Blue driver is available here -- it conveniently hides some of the bells-&-whistles basic users don't need (fan-related options etc).
When its ready, Inovellli will send their latest firmware to Hubitat and Hubitat staff will then make it available to load via Hubitat's own zigbee device-level firmware update option.
I've been using Blues ever since their ill-fated initial launch (oof, there were lots of problems with that original firmware!), and I've done each iterative f/w & driver update they've had thus far... Along the way, some have been better than others, but this latest driver and f/w have been totally solid for me.
