no method for coercing this S4 class to a vector for utilization of mclust

I'm trying to use the mclust method on an .FCS format file (which is a flow cytometry format file) and I read this file into R as flowFrame object.

install.packages("openCyto") # since the old version sefaulted my R session
library( openCyto )
library(  flowCore)
library(  mclust)

 trial1=read.FCS("export_Alcina TregMAIT_AV 10-1974 P1_CD4.fcs") 
 a=as.matrix(trial1)

Editors note: some of these are Bioconductor packages and you should install according to the help pages for that environment.

However, mclust does not accept the .fcs file as a matrix & I tried to convert it to a matrix with the function as.matrix, and I get this error:

Error in as.vector(data) :
  no method for coercing this S4 class to a vector

I've found similar questions where they explain you have to add importMethodsFrom(S4Vectors,as.matrix) into the NAMESPACE of mclust, which I did. I also did importMethodsFrom(BiocGenerics,as.vector) in the NAMESPACE of mclust. However, I'm still not able to use mclust.

P.S. any advice or reading would be appreciated!

If, anyone knows other clustering methods that use GMM model that could accept .FCS format without converting, I'd be very happy.