Unsupported Cisco 7975

[getthelight]

I'm trying to manually configure a Cisco 7975 on the free version of the system (18.0 Update 6 (Built 889)) - this is the linux image.
I'm following these directions and I have used a windows TFTP server to bring the 7975 phone up to 8.5.4 using Cisco's firmwares: https://www.3cx.com/sip-phones/cisco-7940g-7960g/

Therefore you need to ensure that the phones are running this firmware. In case the defined version of the firmware is not installed, manually update the firmware before proceeding. When upgrading a Cisco 79XX IP phone firmware version prior to 8.3.3, you must first upgrade to 8.5.2 before you upgrade to 8.5.4s which is outside of the scope of this document!

1. Download the Cisco 79XX support files. <-Done
2. Find the provisioning folder of your 3CX Install – by default it is something like:
   C:\ProgramData\3CX\Instance1\Data\Http\Interface\provisioning\XXXXXX. <-- Done
   
   Where XXXXXX is the randomly generated folder name of 8 to 12 characters.
3. Place the whole content of the zip into this folder. This bundle will also change your phone to use SIP and updates the firmware to 8.5.4.s.

Step 2: Configure TFTP Server​

Access this guide that shows you how to configure a TFTP server for 3CX. <-- I installed TFTPD-HPA and pointed it to the provisioning folder in step 2. Configured the 3CX server IP as my DHCP 66 option so that the phone would be directed there to look for a TFTP server. Problem... nothing happens here. Not sure how phone would know that it should grab any of these files provided in "Cisco 79XX support files."