What causes a Unity rigidbody not responding to AddForce?

The rigidbody is kinematic (ignores forces), its mass is so high the force is negligible, constraints freeze its movement, or the force mode and magnitude are wrong, so AddForce has no visible effect.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix a Unity Rigidbody Not Responding to AddForce

Quick answer: Make the rigidbody non-kinematic, use an appropriate force magnitude and mode for the mass, and check that constraints do not freeze the movement axis.

A rigidbody not responding to AddForce is kinematic, over-massed, or constrained. Here is how to fix it.

How to fix it

1. Make it non-kinematic

A kinematic rigidbody ignores forces entirely. If you want AddForce to move it, uncheck Is Kinematic. A kinematic body is moved by setting its position, not by forces.

2. Use an appropriate force and mode

A small force on a high-mass body produces negligible movement. Scale the force to the mass, and choose the right ForceMode (Force vs Impulse vs VelocityChange) for the effect you want. The wrong mode or magnitude makes the force imperceptible.

3. Check the constraints

Rigidbody constraints can freeze position on the axis you are pushing, so the force does nothing visible. Confirm the relevant position axis is not frozen in the constraints, or the body cannot move along it.

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.

Ship the fix, watch the signature disappear from the next build. That's how you know it's really gone.