I see the same problem reported recently (March 24, 2019). Previously was able to use ggbiplot for prcomp object. Now I get the error shown below:
Here is my code:
> pca<-prcomp(data,center=TRUE,scale=TRUE)
> library(ggbiplot)
> ggbiplot(pca)
get error:
Error in plot_label(p = p, data = plot.data, label = label,
label.label = label.label, : Unsupported class: prcomp*