Unable to upgrade Zebra TLP 2844-Z printers firmware

I have 4 Zebra TLP 2844-Z printers, 2 have HW version V13.0.0.42, 2 have HW version V18.0.0.42. I upgraded the firmware to V45.11.7z of the 2 printers at V18 with no problem.

However, after flashing the 2 printers at V13 using Zdownloader V2.0.6 (and powering off/on), the fw version is unchanged. I have tried both over the network and with serial connection, the Zdownloader shows the upload progresses just fine. When uploading using the serial connection, the status LED blinks green, when using the network connection it is solid green (I take it this is normal).

My current FW version is V45.11.2a.

The printers appear to function normally, I can point my browser to their IP address and change the configuration/settings, and I can send commands to them using the setup utility and I get a response back from a status inquiry for example.

Any suggestions would be helpful. Thanks!