DHCP Reservation and/or Static IP

I can set a DHCP Reservation on my Goggle Nest home router, to assign my GL-AXT1800's MAC address to a specific IP address. That doesn't seem to work. I can set a Static IP on the GL during the Repeater Connect process. That works. Why would the DHCP Reservation not do the trick? I did set the GL to use the Factory MAC address so it is a known fixed value.

Hello,
Il not sure this is a problem from your glinet router.
It seems to be a problem from the Google Nest.

I have my Flint2 behind my isp box (= router in France , isp provide this kind of router that does provide internet+telephone+tv), and I set the Flint2 in a dhcp reservation in my isp box , on its DMZ so I don’t have to worry about port forwarding between this two.

The flint2 have always the right ip adress I set up in the dhcp reservation in the isp box.