Thumbnails Not loading?

[ChrisLegend]

This use to happen to me as well, it wouldn't appear on my screen but it would appear on everyone elses. Eventually it stopped though and I thought YouTube had actually fixed this bug but it appears not :/

 

[VibrantRecords]

Most likely, it is your internet connection.

 

[PinProject]

Ah yeah sometimes that happens to me but then when I log out and log in again it lets me select a thumbnail.