Fixest - feols() - did

I am trying to add a did structure to the feols() but after implementing:

model_1 <- feols(y~ treat*post+controls-1 | country+years|0| country, data = dataset)

the did estimator spills out NAs. Does anyone know why this could be the case?

Many thanks.

I think we need a FAQ: How to do a minimal reproducible example ( reprex ) for beginners

A handy way to supply some sample data is the dput() function. In the case of a large dataset something like dput(head(mydata, 100)) should supply the data we need.