Why is there no data past three years ago or after three years in the future in my report?
If your report uses predefined date groups, there will be 3-year cutoff period for those dates. To get around this, you will have to create your own custom data items instead of using the predefined date groups. Below is the article about it from Help.
Grouping by Dates in PPM Reports
See the bottom note:
Note: Native Date groupings limit the data returned to three years in the past and three years in the future. If you require data outside of this range, you will need to create custom date filters for your report instead of using the predefined date groupings.