Changing type to beam particle suddenly stops the animation. It becomes obvious after applying a material. You can follow along with this tutorial where the animation stops at time 3:45 and does not animate. I have replicated this in a second particle system. If this is not a bug there is some new approach in 4.20 where a variable needs to be set. Anyone have an idea?
We’ve recently made a switch to a new bug reporting method using a more structured form. Please visit the link below for more details and report the issue using the new Bug Submission Form. Feel free to continue to use this thread for community discussion around the issue.
Just stumbled upon the same issue. It seems like the Lifetime module is ignored for Beam type particles in 4.20, which makes them practically infinite, and also breaks the color over life alpha animation that is present in the default emitter. I have submitted a bug report.
There is a fix for this.
The problem is by default in the editor, when you click on the emitter itself, you need to check Use Legacy Spawning Behavior!