I got this grey keyed 464 in February 11th or so 2020, but never got around to posting about it here.
But, better late than never 🙂
Unfortunately It wouldn’t power on at all.
The motherboard is much smaller than the one in my original colour CPC 464, and the following wiki shows the different motherboards manufactured for CPC’s.
So I took it apart and found a loose connection, and after wiggling it (I’m pointing at the connection), the computer came to life !
This particular CPC was made in Germany using Schneider parts (keyboard and colouring) but made after the partnership with Amstrad/Schneider ended, so they used the parts remaining, in other words the grey keyboard, but with the Amstrad logo.
for details on the keyboard types see here https://www.cpcwiki.eu/index.php/Keyboard_Versions
and for help with non starting CPC’s see here