Under Track and Iteration Status page, it shows less Iterations compared to what we see under Plan --> Timeboxes.
The Iteration Status page Iteration Dropdown list will only display the Iterations for the project you have listed at the top of the page, even if the project scoping at for the page is set to scope up AND down. The timeboxes page dropdown (selector box) will adhere to the project scoping set for the page.
For initial troubleshooting, please check the project for the Iterations that are seen in the timeboxes page to verify that they are the same project that is set in the Iteration Status page. It is possible to sort by the project in the timeboxes page, so that may be helpful for you.
It the above troubleshooting doesn't root cause the issue you are seeing, please send a screenshot of the timeboxes page and the Iteration Status page dropdown.