Test cases showing cancelled in execution test suite.

It depends on how you cancelled, stopped or paused the execution, some actions will not allow you to resume.
Please see this post: https://jazz.net/forum/questions/94303/how-to-resume-the-test-case-execution-if-we-cancelstop-run-in-middle-of-execution

The referenced workitem has more explanations:
https://jazz.net/jazz02/web/projects/Rational%20Quality%20Manager#action=com.ibm.team.workitem.viewWorkItem&id=62649