Hi there! My name is***** am a computer professional with over 15 years of experience with both Mac and Windows computers, phones, tablets, and printers. It would be my pleasure to assist you with this.
Now that you have a new modem, you have new SSID (network name) and password. You will need to change the network settings on your printer to match those of the new modem. There are two ways to do this. Both methods are outlined in the Network User's manual which you can access by clicking on the link below:
This manual is in pdf format and can be saved to your computer for later viewing or printed ( but keep in mind that it is 78 pages).
One of the methods is to use the Utility from Brother called the BR Admin Utility Light. If you will please let me know what your operating system is, I will provide a link to the utility that you can download and install, if you don't already have it on your computer.
If you're not sure, please click this link and tell me what you see: