Lindsey, Chris Are you still blocked? In addition to Satish's suggestions, please see below information.
I have an on prem solution setup and i am trying to license my sensors and they are shwoing as expiring in one day. AFAIK our subscription is paid up and i am unaware of how to get a new license with a longer expiration period.
If your Defender for IoT sensors are showing as expiring in one day, you may need to apply a new activation file to your locally managed sensors. you need to apply a new activation file to locally managed sensors every year. After a sensor's activation file has expired, the sensor will continue to monitor your network, but you'll see a warning message when signing in to the sensor.
If you have versions prior to 10.0, your license may have expired. To activate your license, you need to open a case with support and supply them with your Activation ID number. Support will then supply you with new license information in the form of a string of letters. You need to read the terms and conditions, approve them, and paste the string into the space provided.
You can find more information about activating and setting up your on-premises management console and sensors in the following article: Activate expired licenses
If you're still having issues with licensing your sensors, I would recommend reaching out to Microsoft support for further assistance.
If you need further help in this matter, please comment in the below section and we are happy to discuss!
If this answers your query, do click Accept Answer and Yes for this answer as helpful. And, if you have any further query do let us know by commenting in the below section.