Are you using Tripoto App or website ?
It only works for the Website. Just write your Trip details and add a link from Youtube in the section where you want to add and Publish . Hope it will be done.
Just do it from website, there they have a specific option if you want to link an Instagram ID or YouTube, and once you copy paste the link. It works like a charm .
A few days back I suffered the same problem .The application on mobile phone causes a glitch for such kind of things but the website version on the laptop/ desktop is the best method of linking your youtube videos to your tripoto profile.