--make-grm with --keep not working

I am trying to make a GRM with a subset of my population sample, and have a text file (ex. IDs.txt) with the IDs of the individuals in the subset listed one per line. When I run --make-grm with --keep IDs.txt and the other necessary parameters, it results in an "Error: No individual is retained for analysis.".

Any suggestions on what to do here?

Thanks!