I've already searched the forum to no avail, and I don't know the first thing to start troubleshooting this problem. The IIgs itself works fine through composite out, but the RGB monitor only displays this solitary horizontal line. I just acquired the monitor last month and have been waiting on a cable which just arrived today, so I have no idea if it's the monitor, or the cable, or something else entirely.
Help is definitely appreciated, haha. Thanks!