Hi! When you bind one or more bones to your mesh, Spine will try to calculate the weights based on the bones that overlap the mesh.
(more about this here: http://esotericsoftware.com/spine-weights#Auto )
If only one bone weight is calculated, this may be due to binding the mesh to one bone at a time only, leaving the others out, or the other bones not overlapping the mesh.

If you are sure the bones overlap the mesh, then try to select all of those you wish to be weighted automatically and press the auto button.

If the bones don't overlap the mesh, Spine won't be able to include them in the automatic weight and you will have to apply the deisred weight yourself.

I hope this helps, but in case it doesn't, please consider also including a screenshot of the problem.

Thank you for attaching a screenshot.
I can clearly see that the first bone is not overlapping the mesh, and this can lead the automatic calculation to fail. What happens if you select all bones but the one not overlapping and press auto? (in theory this way it should work)