Doing a factory reset makes it worse. Because you are essentially defaulting the phone firmware to the firmware shipped from factory which I think is 8.3.2....Not all problems are solved by factory reset I learnt the hard way.
To upgrade to the firmware on the 8.5 servers which is 9.X series you need to hop first to 8.5.2. And from there you can jump to 9.X firmwares...
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"The essence of christianity is not the enthronement but the obliteration of self --William Barclay"
As Paolo mentioned, the phone firmware MUST be upgraded to 8.5.2 first before going to 9.1.1 SR1. This is clearly mentioned in the release notes for firmware version 9.1.1 SR1
" For all SCCP firmware upgrades from firmware release versions earlier than 8.3(3) to version 8.5(2)SR1 or greater, you must first upgrade your firmware to version 8.5(2). Once you have upgraded to version 8.5(2), you can upgrade your IP Phone to version 9.1(1)SR1 or later. "
Therefore, it is always a best practice to read through the release notes guide of desired firmware version to avoid such issues. link to Release notes is always present on CCO page from where the firmware can be downloaded.
Hope it helps ?
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