Tests section is not displayed in the Test Plan

Description
Tests section is not displayed in the Test Plan

How to reproduce

1. Create a Test Plan
2. Add Tests

Actual result/Attachments
The section of the Tests prints the number but nothing more than that:

Expected result

Version

• 6.5.1

PS: Additionally, when creating a Test Execution from the Test Plan, the fresh Test Execution doesn't have any Tests or neither it linked to the Test Plan