It’s a little tricky to find the MavTV shows on trials that have been archived. They currently have the indoor national posted, plus NATC rounds 1-6.
I’ve found that the best way is to:
1. From the homepage, click the Watch Now navigation tab at the top
2. At the bottom of the Watch Now page, select the Motors channel.
3. Click the ‘search’ link in the right sidebar and type ‘trials’ in the search box
4. Select one of the trials shows on right sidebar; use the internal scrollbar to see them all.