Need to do few things to identify the problem.
1. You can give some screenshots of your source data file that show each table has some data.
2. than, create a new power bi file and import one data table at a time, and check whether you have data or not.
3. If all tables data are shown in the data view tab then go for table relationship creation. [do not create multiple relation in taables]
4. As if you do not get the data yet, you could reinstall power bi or report the problem to power bi.
Let me know, what is the progress?