Hello @rjclaxton and welcome to Trend Micro Community!
For you to renew your subscription for 1 device, you need to purchase the Trend Micro Antivirus+ Security. It is a different program from Maximum Security. Once you purchased it, you have to install the correct program on your device,
You may click herefor your reference to our online store.
Thank you for choosing Trend Micro and have a great day! :)