Confused about when I start?

Hi so they told me I got the job a few days ago and I did some tasks on workday but can't log in to that anymore so I assume that's all done, they sent me a another link to more tasks to do which the deadline for is 3-4 weeks from now so I'm not sure how relevant those tasks are to when I start and none of the emails or passwords work though so should I leave that alone till I have a point of call with someone who I can bring it up with or do I need to complete the tasks before anything else happens. When did they let you know your actual start date?