Quick answer: Enable Loop Time on the clip, ensure the animator state loops, and check transitions do not exit the looping state prematurely.
A Unity animation not looping is the loop setting or a transition. Here is how to fix it.
How to fix it
1. Enable Loop Time on the clip
The animation clip has a Loop Time checkbox in its import settings. If it is off, the clip plays once and stops. Enable Loop Time (and Loop Pose if needed) so the clip loops.
2. Check the animator state
Even a looping clip will not loop if the animator transitions out of its state. Ensure the state is meant to loop and nothing transitions away at the end. A transition with exit time at the clip end stops the loop.
3. Avoid premature exit
If a transition's condition is met, it exits the looping state. For a state that should loop indefinitely (idle, run), ensure no transition fires while it should keep looping, so it does not cut to another animation.
Catching the ones you can't reproduce
The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.
Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.
This is where a tool like Bugnet earns its place. Its SDK captures every Unity error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.
The bug you can't reproduce isn't gone — it's just invisible until you capture it from the player's device.