Hi @chu_man_ho
Welcome to Trend Micro Home Users Community!
There is no need to reinstall the Trend Micro after renewing your subscription. If you do see a download now button that is just in there in case that the Trend Micro is not installed on the device.
Once you have renewed your subscription please make sure that the device is connected to the internet then open the Trend Micro app on your device for the expiry date to update automatically.
Hope this helps. Let me know if you need more help.
