Weight painting has no weight

Hello. I want a very simple rig for my character, but there is an issue with weight painting.
The colour of the paint doesn’t seem to influence the mesh. Where there is paint (of any colour except blue) the influence on the mesh is 100%.

I have tried rigging a simple character in the same scene and it works fine.

Any ideas? Thanks in advance.

It’s probably that vertices aren’t weighted to multiple bones.

If you weight a vertex to only a single bone, that bone will have full influence over that vertex, regardless of the strength of the weights. Effective weights are a function of the relationship between mutliple weights.

That makes sense. But the same thing is happening with multiple bones.

It doesn’t matter if it’s happening with multiple bones-- it matters whether a particular vertex is weighted to multiple bones.

If you link a file, I’ll look at it.

Of course! How silly of me.
Thank you so much!