M700 update fail

Good evening to all,

We have a main base M700 and 2 secondary bases. We also have a single connected M65 phone (yes  that's true !)

The current firmware is IPDECT/04.10/B0014/20-Feb-2019 11:43

I am looking to upgrade the firmware to 450/ 11 and I have the following error message in the logs: Base FWU ended with error code 2157 (HTTP_GFT_SERVER_UNSPECIFIED): HTTP protocol

I tried to upgrade from our own server by putting in the necessary files but I still have the same error below...

Your help is welcome.

Have a nice evening.

Julien