What exactly are you trying to "loop"? If it's a link on the page to a video, click on the video thumbnail to highlight it and then click on the "object" tab to the right, then click on "animate thumbnail".
At that point, from the "main menu" page, figure out how long you want the clip to play for. eg. auto-calculate length or choose your own.
I'm trying to loop video or a clip on the main menu, not an object. I can get the video clip to play but it always runs out when it's over and I'd like it to keep starting over. When I click loop or try to select time on page properties it doesn't seem to apply it.
I presume you are wanting a clip to play as a "background video" on the main menu page.
I opened up the folder from page properties and directed which file to play, clicked loop and it played as expected including the looping via preview. So, I'm not sure what else could be causing your problem.
I experienced what you were seeing. Do you have audio associated with your background? I found that the audio was longer than the video, so it looped only when the audio was finished, leaving a black screen until the audio finished. I did one of 3 things to fix:
1. Shorten audio to match video. Clunky, feels weird when audio abruptly restarts.
2. Uncheck auto-calc length box. Set length to video length. Same result as #1.
3. Edit video in vegas to repeat n number of times, where n is the ratio of audio to video lengths.