Sprint Tracking page will not load for certain Sprints on the Agile Board even for Current Sprints.
This was happening because you have customized the State field to be a Dropdown with --None--.
When the Visual Task Board was being built in the code, it was failing since None was being added as a State which does not exist and the Agile Group Vtb Board record would never get created.
To update the dropdown type, follow the steps below.
1. Navigate to System Definition > Dictionary
2. Search for and go to the record with the Column Name of "state" and the Table of "task"
3. In the Choice List Specification tab, change the Choice field to "Dropdown without -- None -- (must specify a default value)"
4. Save the form