After BIOS update no connection or timeout

[sega]

In the start of the week same of our PCs suddenly got an error. After the FOG start menu we got this error:

Starting bootmgfw.efi
Using load options ''
Secure Boot validation failure loading bootmgfw.efi!

Our PC support told us to update our BIOS because of new signatures (Starting directly on Windows without FOG in between gave us also a Invalid signature error). After the update we can boot into Windows, but now we have problems booting into FOG.
It’s loading the NBP file and iPXE is starting, then we getting the following error

iPXE 1.20.1+
Configuring (net0 xx:xx........) .......... No configuration methods succeeded (http://ipxe.org/040ee186)
Configuring (net0 xx:xx........) .......... No configuration methods succeeded (http://ipxe.org/040ee186)

After that I go into the PXE shell and try typing dhcp. This gives me an “OK” always after the 2nd try. So im again in the FOG starting menu and want to boot into Windows and I’m getting the following error:

http://......... refind.conf ......... Connection times out (http://ipxe.org/4c0a6092)
Could not boot: Connection timed out (http://ipxe.org/4c0a6092)
Could not boot: Connection timed out (http://ipxe.org/4c0a6092)

Our setup is:
Your version of FOG is up to date.
You’re running the latest stable version: 1.5.10
Custom signed files with this tutorial: https://forums.fogproject.org/topic/15888/imaging-with-fog-and-secure-boot-poc
Changed from ipxe.efi to snponly.efi didn’t helped.

Someone knows what’s the problem here and how to solve it? Do I need to update the FOG server or just update the pxe file?

Thanks in advance