I cannot update my 3 device subscription onto my iPad & iPhone. Need assistance. Have tried your direction but doesn’t work
 

Hi Vicki Birch, 

Welcome to Trend Micro Home User Community! 

May we know if you encountered any error messages while updating the app? If yes, please provide the screenshot here so we can further investigate.

You may also follow the steps provided above on how to update your Trend Micro Mobile Security: 
Update Mobile Security on iPhone & iPad: Step-by-Step Guide
How to get the latest version of Mobile Security on Android

Hope this helps.