Fama Macbeth panel data regression: "Insufficient number of time periods"

Hi

I am having trouble with Fama Macbeth panel data regression:

fama <- pmg(excess.return~rmrf+smb+hml+rmw+mom+rsi+roc+bidask, data, index="Dato")

R gives me error message: "Insufficient number of time periods".

Can you help me with this error?

Thanks