Firmware Upgrade - Invalid Module Header!

[AnnaKili_apc]

Hello,

I was attempting to upgrade the firmware on two of our web cards to v6.8.8 using the firmware upgrade utility.
Ugrade seems to have been installed incorrectly/incompletely, because I can't log in to the web interface anymore. I get the following error message:

The Application Was Not Able to Load
You are attempting to access a Schneider device.
There was a problem loading the application. Please login to the device via telnet for more details."

I opened up a telnet session to the UPS:

Application Module
---------------
Invalid Module Header!

APC OS(AOS)
---------------
Name:                  aos
Version:               v6.8.8
Date:                   Apr 28 2020
Time:                   17:21:52

APC Boot Monitor
---------------
Name:                  bootmon
Version:               v1.0.9
Date:                   Mar 27 2019
Time:                   16:23:06

When I start the upgrade again with the tool I get the error:
Could not retrive configuration file via this method; please recheck settings

The manual FTP upload does not work either:
C:\install\APC_MMC_Firmware\Bins>ftp XXX.XXX.XXX.XXX
Connected to XXX.XXX.XXX.XXX
421 Service not available, closing control connection.
Connection closed by remote host.

apc>ftp
E000: Success
Service:        enabled
Ftp Port:       21   

Any suggestions on what I could take a look at?

Thanks,

AnnaKili