The new tab burst doesn't get loaded for me anymore for the last one/two days. Tested only on macOS 10.11 & 12. There is a similar bug 1399101 for windows 10, difference is, that the animation doesn't show for me at all anymore. Also the throbber doesn't change color from grey to blue anymore, but that might be a different bug.

Do you have any steps to reproduce this? Without that there isn't much for me to go on.

Hey jaws, sorry I don't have any, and the animation reappeared today on 10.12 as nothing ever happened. On 10.11 I just tested with add-ons disabled and now it works either way again. As it doesn't seem to be a constant issue (if still any) after all, I will mark it as dup of 1399101. In case it comes back and I can reproduce something I will comment over there.