Cisco 7841 MPP/3PCC Phone stuck on reboot loop

[cisco20202020]

I just did 

phone's IP address/admin/resync?https://cloudupgrader.webex.com/Cisco/Upgrade/$MAU/$SWVER/$PSN.xml

on a Cisco 7841 MPP/3PCC phone and now this phone is stuck in an infinite reboot loop! The phone was on firmware version 11-1-1 It has been plugged in for 24hrs and still rebooting. I have tried unplugging and plugging back in and waiting several times, no luck at all.

I ran the above link after factory resetting the phone.

This is odd because I ran this exact procedure on another identical 7841 phone that was on the same 11-1-1 firmware and it upgraded the firmware too the newest version without any issues at all.

I have tried doing the factory reset procedure (unplug, then hold # and plug back in .... followed those steps, it doesn't ever show me the reset options).

What can I do to solve this? Before running phone's IP address/admin/resync?https://cloudupgrader.webex.com/Cisco/Upgrade/$MAU/$SWVER/$PSN.xml there were no issues with the phone at all.

[Geovani]

Hi, 

Are you able to login to the phone before it reboots? Can you take any logs? 

I would try again performing a hard factory reset with the key sequence. If you're able to to login to it, you can do a url factory reset IP_Address/admin/advanced/direct-factory-reset 

[cisco20202020]

I have been trying to do all of this, no luck at all. It doesn't even get to the point of obtaining an IP address. It basically ignores the factory reset key sequence when I do it. And it's not possible for me to do it via URL because it doesn't even get an IP address. Any other things? Otherwise it looks like Cisco destroyed my perfectly working phone, with the new firmware...

[Geovani]

Are you able to take a pcap at switch level? would be interesting to see what the phone is sending/receiving. I have not seen this happen before. 

[cisco20202020]

Ok I have been trying again and this time, finally after holding the # key for almost a minute and then immediately pushing the reboot sequence 1,2,3,4,5,6,7,8,9,*,0,# and waiting for few minutes, it worked and upgraded to the latest firmware. It was very odd that it took so long and I had to factory reset it this way to get it out of the reboot loop.