Chic,
I loaded your file into Wordpad and then saved it to my computer as a plain text file, then loaded it into PicSender, and it loaded normal. The M7 at the beginning of the file is causing the error. I removed it and reposted your file.
To use an M7 command, I think it has to be enabled in the grbl source code and then recompiled. Seem to remember reading something about that somewhere a while back.

- test file.jpg (79.83 KiB) Viewed 1228 times
John
BTW, I have not run the complete file. Please let me know if this takes care of the issue for you.