Hey John,
I can’t say exactly why your file was not working, it gave me a memory warning when I tried to run it! I rebuilt it in both OptiMode and OptiBPM and it works fine. Attached is the BPM file, if you don’t have the same version I would say just try rebuilding the file from scratch. I only needed a mesh of 200×200 to find modes in the n = 1.8 case.
Regards