Unable to connect travel router wireguard client to my flint home router wireguard server

Hi everyone, my flint and travel router were all working fine, unfortunately i had to change my modem due to internet issues. after I changed my modem, I have connected the same flint router, but after connecting, my travel router is showing wire guard client with yellow/orange light and not getting connected to my flint wire guard server. Please someone suggest me, as I have tried all the possible options and I need this travel router to be connected for me to travel away

Hi,

Did you set-up the home router (Flint) and the ISP modem follow this guide?

Did you enable the port forwarding in the ISP modem?
Does the ISP modem have the public IP?