Can't get airport express to connect to internet after ISP changed my modem

Hi. My internet service provider installed fibre optic to my house, so they gave me a new modem. Have not been able to get airport express to connect to the internet ever since. Just get the flashing amber light. Other than paying $50 for phone support, I have no idea what to do. I just use the airport so I can play music from iTunes from my stereo using airplay. I use the airport utility on my laptop.