plm/fixed effects models: fixef function error - wrong effect argument

Question

I am using the plm function to analyze a large dataset with 120,000 IDs over three years. My specification looks the following:

h1b2model = plm(value ~ daysexisting2 + mgm_acquired:daysexisting2, 
                index=c("number", "year1"), 
                model = "within", effects = "twoways", data = Longpd)

It gives me an output which is consistent to the lm outputs. However, the lm does not accept my large dataset (vector memory issues). Thus, I am using plm but when I am trying to extract the year-specific intercepts, the fixef function gives me the following:

fixef(h1b2model, effect = "time")
Error in fixef.plm(h1b2model, effect = "time") : wrong effect argument

Does anyone know what to do? Including year dummy variables into the plm function seems to be wrong as well, as I only receive one coefficient.

Thanks in advance!