Blender | Can’t Choose a Bone…

I couldn’t get bone selection to work properly in Weight Paint mode, so I wrote down how to fix it.

Prerequisites

Blender: v4.0.2

Contents

Choose the object, then the bone, in that order.

Choose Object > Parent > With Automatic Weight to apply automatic weights.

Checking in Weight Paint mode, you can see it’s turned red.
But I still couldn’t choose a bone with alt + left click…

The cause was that I had the selection order wrong before entering Weight Paint mode.
The correct order is to choose the bone first, then the object.
It’s an easy mistake to make, since it’s the reverse of the order used when building the parent relationship.

In the end, I was able to choose the bone.

Conclusion

When building the parent relationship, choose in the order: object → bone.
When in Weight Paint mode, choose in the order: bone → object.