csdid error 3598

[Henry Strawforrd]

I am using the great user-written command https://friosavila.github.io/playing...ain_csdid.html

When running a regression I received the following error

Any ides what this matrix is and why it is missing? I checked the outcome and it only takes the value of 0, thus has no variation. Might this be the reason?

[FernandoRios]

Not sure.
Can you share a reproducible example?
Otherwise its hard to figureout what is happening.