Based on your response, I would wager to say that it’s the video file your Final Cut system is trying to play that’s causing you issues.
What format of video are you trying to play through your system and what format is the sequence you’re dropping this video in set to?
If it’s not Apple ProRes you could try transcode it to this format or even possibly just run it through compressor using one of the ProRes format presets making sure to transcode both the audio and the video. Then try opening those files in Final Cut and see if you still get the spinning wheel.