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Your CCS picture from the pdf link shows two lines with red highlighting on the left near the breakpoint circle. This indicates that this line was changed recently. You should re-build and re-load the program so that no lines are changed to make debugging useful. The debugger only understands what was in the source when the last build occurred, so any changes will confuse you as to what the debugger is trying to debug for you.
The message box says "Cursor is not on a valid line". This is referring to what the debugger thinks is valid based on the most recent build. Any changes you have made since that time are invalid to the existing build/load.