Once you go to the MVC site via Vistana.com, select Book Vacation Points Club. Now on the URL, you can see your MVC Owner ID as "VSE&ownerId=0000000000000" A Few months back, I created an MVC account with a User ID and PW on (
https://owners.marriottvacationclub.com/timeshare/mvco/club-resorts ) but was unable to continue the setup until I could provide a good MVC Owner ID. Well, I used the VSE&ownerid I found on the URL and was granted access. Anyway, this is probably too much work to get the same information logging via vistan.com instead of going directly to MVC. I am used to doing this kind of thing due to my job.
A small caveat, this works most of the time but it looks like our MVC accounts are not super stable yet.