Optiplex 990 Bios Update A23

Hello,

I tried to update the bios from a20 to a23 but i doesnt work. There is no error message.

i was asked if i will flash the bios from a20 to a23, it loads the files and the pc starts new...without doing the update.

i tried it also to update form usb but the same. pc starts new without flashing the bios.

to install a20 again doesnt work too

Whats wrong?i Need to update to a23