Sub Domain Not Tracking In Google Analytics

For the first time, I am using an subdomain instead of a I can’t figure out why the subdomain is NOT tracking in Google Analytics despite the tracking being set up correctly in Unbounce through the script manager.

I added a secondary dimension to the google analytics to see subdomains and I still only see the main domain, none of the subdomain I am using.

Can anyone shed any light on why this subdomain’s data is not being pulled through to Google Analytics? Thanks!