Only thing I see via my Google skills is this on the Favero website…
"Assioma has a Bootloader mode that safeguards the operation of your power meter in case of unexpected events while updating the firmware (e.g. sudden shutdown of the mobile phone). Assioma enters this safety mode by deactivating all non-essential functions, including LED lighting. Assioma might seem off but actually is waiting to be restored through the Favero Assioma App.
To restore all the functions of Assioma, go to the search section of the Favero Assioma app, find the device in BOOTLOADER mode (indicated in red) and press on the “RESTORE” button. Once the recovery is complete, you can restart the firmware update.
We recommend restoring Assioma as soon as possible. However, if you want to postpone the operation until later, remember to leave your Assioma in charge.
If you still have a problem with your smartphone, we recommend you try another smartphone model or tablet."
I also changed the device and it appears to me when I connect locked for both pedals and I can’t enter the settings! can’t find bottloader mode! 
I assume you have contacted Favero Support?
I sent an e-mail, I’m waiting for an answer!
I haven’t done the latest software update and this now has me scared. Will be following for updates on a resolution. Good luck.
As my experience, there was an easy way to reset firmware(just using a magnetic connector of charger, that was instructed by favero after service. But finally you still need favero to read your power meter error log.
I also tried this variant without any result!
What did favero support say?
I can’t find the documents anymore and without them I can’t advise myself
I’ve got the same issue, Favero Support recommended to order new sensors.
Can’t find how to reset with a magnetic connector. Looks like all this instruction was removed from the official site.
I found this on the Assioma thread over at Weight Weenies. No idea if it works but might be worth a try.
This is the resseting firmware procedure:
Restart the internal firmware of the sensors by completing the following steps:
1 - Disconnect the magnetic connector from the USB cable (considering in this case that you are using one magnetic connector for the recharge, you need to use the second one for the suggested operation)
2 - Place and keep in that position the magnetic connector on the plastic case of the sensor, where it is reported the text “FAVERO Electronics”.
3 - Wait at least 15 seconds, always keeping the magnetic connector in that position (in the meanwhile you should see that the LEDs will switch on one by one and also all together)
Thanks,
Unfortunately reset didn’t help
Care to elaborate how the sensors became locked?
I thought they could only be locked remotely by Favero - before a new pedal was sent as a warranty replacement in my case. The lock request came through and I had to confirm it before they sent a new sensor out to me.