At first I received an error when I ran require(data.table) indicating it could not be found and I was unable to download data.file, but I was able to install it with the command

install.packages("data.table", type = "binary")

Now my output is:

> require(data.table)
Loading required package: data.table
data.table 1.12.8 using 2 threads (see ?getDTthreads).  Latest news: r-datatable.com
> sessionInfo()
R version 3.6.3 (2020-02-29)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: macOS Catalina 10.15.7

Matrix products: default
BLAS:   /Library/Frameworks/R.framework/Versions/3.6/Resources/lib/libRblas.0.dylib
LAPACK: /Library/Frameworks/R.framework/Versions/3.6/Resources/lib/libRlapack.dylib

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] data.table_1.12.8

loaded via a namespace (and not attached):
[1] compiler_3.6.3

I might be jumping the gun here, but I then tried the script again and it still didn't work. I've then starting playing with the code to see if I could obtain an error. I now have an error to work with,

Error in if (len%%wd != 0) errex.AFNI(paste("The content under -dataTable is not rectangular !",  : 
  argument is of length zero
Calls: process.LME.opts
In addition: Warning messages:
1: In if (!is.na(lop$qVars)) lop$QV <- strsplit(lop$qVars, "\\,")[[1]] :
  the condition has length > 1 and only the first element will be used
2: In if (!is.na(lop$qVars)) lop$QV <- strsplit(lop$qVars, "\\,")[[1]] :
  the condition has length > 1 and only the first element will be used
Execution halted

I've since spent my time trying to figure out where missing or extra spaces could be and searching old errors on the afni message board and working in sublime text where I track exactly where my spaces are and are not. I saw a similar error and tried to follow the instruction to use file_tool to track down the source of the error.

file_tool -infiles test.sh -test
test.sh has 0 bad characters

test.sh file type: UNIX

This might be irrelevant if there were more I was supposed to do after the steps you asked above, but I wanted to include just incase.

Thanks again!