No Requirement Links when I open a test case
One answer
If you are in test case browsing mode (Construction -> Browse Test Cases), just make sure you have "Validates Requirement" column selected, then you should be able to see the linked requirements there.
Since you mentioned that you "opened" a test case and you were trying to find "Requirement Links" section, I assume that you would like to start the Requirement Reconcil process to find modified requirements and mark the test case as suspect as appropriate.
If you are not able to find "Requirement Links" section after you open a test case, chances are, it is not there (isn't this obvious? ;-) ).
You can do the following to get it back:
1. Click on Manage Sections
Note: Show All Sections in above screenshot means Show All Selected Sections, not Show All Available Sections, so if you tick that, it still will not show Requirement Links.
2. Select "Requirement Links" in Available Sections
3. Click on Right Arrow to move "Requirement Links" to Selected Sections
4. Click on OK