TRIM function or CHAR function? Or something I cannot figure out!

Hello,
I have thousands of row of data containing time. I need to know the length of time for a certain task. I have the start and finish times in two separate columns (Column A and Column B) but for whatever reason, the start time is not being recognized as time, unless I manually go into each cell in column A and delete a leading space, that doesn't even seem to be there. Please see attached.
If I place my cursor in front of the first number of the start time and press backspace, then enter, the text gets recognized as a time, and then the calculation is complete in column C. But unless I manually go in and press backspace for each start time, the length of each task cannot be calculated. I have tried everything I know and cannot seem to figure this out. Could someone please assist me?
I have tried TRIM, SUBSTITUTE, etc.