nlme package for Multilevel approach

Question

[khn]

Hello

I am using library(nlme). What is wrong with this?

fullModel <- lme(A ~ BCD*E, random = ~1 | Subject/B/C/D/E, data = data2,method = "ML")

Error in MEEM(object, conLin, control$niterEM) : Singularity in backsolve at level 0, block 1

Thank you so much!!