"This browser does not support video playback." Playback limit of some sort?



I developed a Twitter bot that tweets a video every hour. More precisely it tweets a link to a random video previously tweeted by the same account, so I upload a video only one time, just to make things easier.
I tested it while the account was still locked and everything worked perfectly, but when I opened the account me and everyone else started to get the error “This browser does not support video playback.” on almost every video, even though they worked before. I was about to give up when I found another account that does almost the exact same thing with hundreds of videos that load perfectly. The only differences are that it tweets only a few videos per day and it has thousands of followers.
So… what am I doing wrong? Is one video per hour too much?
Thank you.