Hello,
I am trying to do a moderation analysis for a regression analysis which worked out perfectly well. However, doing the moderation and adding the moderator returns the messages:

note: 3bn.psa is probably collinear with the fixed effects (all partialled-out values are close to zero; tol = 1.0e-09)
note: 3.psa omitted because of collinearity

and the result table includes '0' for omitted.

The original regression command was:
reghdfe fundflows dummy 5 dummy1, vce(robust) absorb(Individual fund)

The moderation command is:
reghdfe fundflows i.dummy5##i.psa, vce(robust) absorb(Individual fund)

I tried to do the moderation command without FE (i.e. with noabsorb) which worked out, however, the outcome values changed their signs.


What is the problem with my moderation?