Itunes won't let me add and play video files

I been trying to fix this for like two days with no result.

• When I click on a file>open with itunes it'll only open itunes but it won't play the video.
• The video is mp4 and I have tried with other formats.
• I also try going to file>add file to library and it just won't open it.
• I tried dragging the video into itunes folders and the library but it'll will only show the blue highlight.
• I tried reading here and other forums but I guess my problem is not the same.

Thank you in advance.