Error in Difference-in-Difference method

[Brahim KHOUILED]

Hi everyone,
I have panel data

When I run the DID estimator,

I get the following message

invalid group specification
None of the groups defined by id is a control.
r(198);

Where is the problem, please?

[Jared Greathouse]

There's no unit that's never treated (all units are at some point treated). Thus, there's no group from which to construct the counterfactual. I'm okay with using "ever treated" units as comparison units IF there are at least 2 pure controls, but you ain't got that.

[Brahim KHOUILED]

Very clear!
Thank you very much, dear Jared