I have a 2015 lexus 350 and have xm radio, but can't get traffic or weather alerts, screen says "must have active xm subscription" when trying to see alerts.. I have xm radio in my car so can't figure out why the car doesn't recognize this

 

That's weird. The US cars use HD radio to get traffic and weather. Maybe there is a config that's off in your settings.

 

I also live in VA and with my mom's 15 RX350 F sport, the same thing happens. The car is equipped with HD radio and XM but only could get the weather and traffic to work when there was an active XM subscription. I think there is an option in the infotainment menu that enables the updates through an active XM subscription. I believe only certain models in the 15 model year actually could use HD radio for these updates. 2016 and newer models use HD radio exclusively for updates but also offer XM for satellite radio purposes only.

 

Check to insure you have HD Radio in your area. https://hdradio.com/

If you do, tune to the station listed on the website and insure the HD icon is lit on your station list once tuned to the station on your MFD. If it is, you should be getting weather and traffic information updates.

 

Download and configure Lexus Enform App Suite, unlike Lexus Enform Safety Connect/Navigation Assist it is free.
Sign in with Name etc. and then tap center console/Menu/App Suite. First time will involve the phone app updating
the car app but then you are rockin'. Music connections are the least interesting, the Navigation features are the
real reason to use it. Oh, and by the way, LEAS will update your real time Traffic and Weather Channel info!

 

Even if HD radio is available, I think it does not necessarily mean weather and traffic are also available in the area you are located in.
In my area, Knoxville, TN, I listen to HD radio and cannot get traffic and weather for my area.
When traveling back into town, I have traffic and weather for current location, then after zooming out in navigation, traffic is still not available in Knoxville.