Welcome to Justanswer.com, my name is ***** ***** I will do my best to assist you.
When you say "express app" , are you referencing Garmin express? Please clarify.
Also, Click the apple sign at the top left of your screen, then click about this mac. And then where it says version, send that to me as a reply.
and if it is Garmin express, I also need to know the full name brand and model of GPS you are trying to use / update.
Dustin S.Senior Technician and Network Switching Systems Operator / Maintainer.