The queue shows videos waiting to start, videos currently being processed and videos that have finished processing.
Use the queue button in the main iFlicks window to show it. The queue also becomes visible when video processing starts.
Check a video's status before deciding what to do next. A waiting video has not started processing, while a failed or cancelled item needs different attention from one that completed successfully.
For an unexpected failure, note the exact error and the selected preset. Check whether the output file exists and can be played before discarding your source file.