Found the solution – Thanks to everyone who helped!
Now just because in the future others may have the same problem after updating the 5XXX series IP Phone firmware, here is exactly what you need to do to fix your phone so you can access and configure it via HTTP (port 80).
IMPORTANT: Do not update your firmware to beyond Version 06.05.00.08 or you WILL lose the ability to access HTTP access to your phone! If you have already done this, you may have found your way to this page so here is the full solution...
ON THE COMPUTER1) You will need to downgrade your Firmware to 06.05.00.08 or earlier
2) Download the firmware package provided by johnp (GM) from
https://drive.google.com/file/d/1KM8i94DE7sOXnyGPLTHeCcycG-mvxpXU/view?usp=sharing3) Download SolarWinds TFTP server from
https://www.solarwinds.com/free-tools/free-tftp-server4) Install TFTP server onto a system connected to the same LAN as the phone
5) Create exceptions for the following two applications in your firewall (Windows example)
a) C:\Program Files (x86)\SolarWinds\TFTP Server\SolarWinds TFTP Server.exe
b) C:\Program Files (x86)\SolarWinds\TFTP Server\TFTPServer.exe
6) Open the “tftproot.zip” downloaded in 2)
7) Extract the contents (not the tftproot folder) to C:\TFTP-Root which holds the data for the TFTP server
Run SolarWinds TFTP server. You can tweak this if you feel the need, but it’s not required
9) Find the IP address of the computer running the TFTP server and write it down. You will need it
ON THE PHONE1) Power on holding down Volume UP/DOWN buttons
2) On Network Settings press # (No)
3) On Network Parameters press #
4) On Hardware Config press #
5) On Phone Mode press * (Yes)
6) On Protocol press *
7) On Phone Mode press * (Change)
On Phone Mode press * (Minet)
9) On Phone Mode press # (Accept)
10) On Store Changes press *
11) On Reboot Now press *
12) While phone is rebooting, hold down the “7” key
13) After the phone has booted, On Config Teleworker press *
14) On Delete/New press # (New)
15) On IP Address Type press * (IPV4)
16) Enter the IP address collected at 9) in section On The Computer
17) Press Volume DOWN button to proceed
18) On Store Changes press *
19) Phone will now reboot, connect to your local TPTP server, download the firmware and install it
20) After the firmware is installed, the phone will reboot so hold down Volume UP/DOWN buttons
21) On Network Parameters press #
22) On Hardware Config press #
23) On Phone Mode press * (Yes)
24) On Protocol press *
25) On Phone Mode press * (Change)
26) On Phone Mode press 0 (SIP)
27) On Phone Mode press # (Accept)
28) On Store Changes press *
29) On Reboot Now press *
30) After the phone has booted it will be in SIP mode
31) Press the Volume UP/DOWN buttons then let Volume UP button go
32) While still holding the Volume DOWN button, type 2,3,4 on the number pad and let go of the Volume DOWN button
33) On Network Settings press #
34) On Network Parameters press *
35) On View Current Values press *
36) On View Current Network press *
37) Using Volume DOWN key, scroll to Phone IP Address and write it down
ON THE COMPUTER1) Open a Browser
2) Type the IP Address collected at 37) above into the address bar and press ENTER
3) Enter the Username admin and the password (model number of your phone, eg. 5320e)
4) You should now be logged into your phone in SIP Mode
Hopefully, this works to help you regain HTTP access to your Mitel 5XXX series IP phone. There may be some slight variation in the instructions for some models, but these should be enough information to help you get it done.