When you open the Minecraft Launcher can sometimes think you do not own Minecraft, making the play button switch to "Play Trial",

Then after a second, it switches to "Play" the one where you have a legitimate copy

Footage, uploaded onto YouTube due to it being over 10MB: https://www.youtube.com/watch?v=U0ftg8LPXIA

I recommend putting the video quality 1440p, or 2140p (4K) to see it clearly. Also, there's more information on the video description.