First thing to try. Have you power cycled the WL connected device? What is it? What kind of logger are you using? USB or Ethernet?
Reset the data logger.
Check weatherlink.com to be sure it is up. May be a coincidence that you just got modem changed.
Is your firewall blocking the connection?
Where else do you send data? Just to CWOP? Or do you send to Weatherlink.com also? What about WU? Do any of those work?
Next thing to try. Often some wireless network devices don't like when the router or main access point is changed. Even if you kept the same WiFi SSID on the new router/modem. My advice would be to reset the WL device and reconnect it to the network. I'm guessing you are probably using it on WiFi. That is but one guess. What else does the WL system do? Is it on the Internet for other things? This would be pertinent if using USB logger.
Make sure you don't have some other old WiFi router/access point device still powered up that is not connected to the Internet.
Make sure if your modem is in bridge mode that you don't have the WL device connected to an extra modem port. If the modem is in bridge mode (what you should do when you use your own router) then those extra modem ports do not work. So if using Ethernet only the one modem LAN port works (for your router WAN) and everything else on Ethernet needs to be plugged into your router.
There are numerous other possibilities. What would really help is to know more about your network setup.
- who is the the ISP
- what modem model you have
- are you using your router for WiFi or is the modem also acting as the router and WiFi, if yes then router's model.
- how is the WL device connected, WiFi or Ethernet
- what weather software are you using?
- what is the internal LAN address space used: 192.168.x.x or 10.x.x.x and what is the subnet mask 255.255.255.0 or 255.255.0.0 or 255.0.0.0 or something else.
- What is the router's IP internal address.
- what is the IP address of the WL device and is it using DHCP or Static
- what is the distance between WL device and WiFi access
If you don't know how to find some of these answers then let us know and we'll guide you in how to get them