IP Phones go to Unprovisioned State
The common reason for a phone to go to the Unprovisioned state is due to the lack of the correct syntax in the OS79XX.TXT file. The OS79XX.TXT file must only contain the name of the file that you attempt to load, without the .bin extension.
If you convert from SCCP to SIP and the version you attempt to load is SIP 2.3 software or earlier, the OS79XX.TXT must be in the format of POS3xxyy . For example, if the SIP software version is 2.2, the file must contain POS30202.
If you convert from SCCP to SIP and the version you attempt to load is SIP 3.0 software or later, the OS79XX.TXT must be in the format of POS3-xx-y-zz . For example, if the SIP software version is 7.4, the file must contain POS3-07-4-00.
If you convert from SIP to SCCP, the OS79XX.TXT must be in the format of P003aabbccdd . For example, if the SCCP software version is 7.2(3), the file must contain P00307020300
source: Converting a Cisco 7940/7960 CallManager Phone to a SIP Phone and the Reverse Process