I'm not sure how to force DCHP on the router.
Given that noone here knows the model of router you have been supplied with, there probably won't be an easy answer...
However, in my experience it would be really unusual for a home network 'router' to be shipped out without dhcp being enabled.
(How are all your other devices coping? How is their IP address assignment managed?)
As background. There are 2 things going on here, and both need to work correctly.
First, the radios in the RPi and the wireless part of your router need to recognise each other and undergo authentication so that they can 'associate.' That gives you a connection with the potential to exchange IP data.
Second, for any form of IP communication to take place the end-user device needs an appropriate IP address. Usually in a home network such an IP address is allocated 'automagically' by a dhcp server in the network in response to a request from a dhcp client running on the end-user device.
A thought that has just come to me while typing...
In addition to the change to wireless bands, maybe the replacement router is configured to use a completely different IP address range? Devices that use dhcp automatic configuration will pick this up and work as expected. If you have a static address configured into your RPi OS perhaps it is now simply wrong and inappropriate?
I second the advice to experiment with letting your RPi request an IP address from the network infrastructure via dhcp.
Statistics: Posted by B.Goode — Thu Nov 14, 2024 1:54 pm