The 290X can only support a maximum of two passive display connections, HDMI/DVI etc. THe third monitor and beyond will need to use an native displayport connection or an displayport - active adapter - passive connection.
This video will explain the limitation.
Appreciate your willingness to help. However, having to have two passive connections and one active connection hasn't been true for several generations of GPUs. That technology is several years old.
As I stated in my original post, I ran 5760x1080 with three PASSIVE connections with no problems for over a year. I gamed, browsed the web, created spreadsheets, watched HD porno, etc. etc. with no problems. One of my monitors died (RIP) so I bought three new 144hz, 2ms 1080p monitors and now for some reason one of my monitors is not getting signal. I've swapped cables, monitors, etc. but to no avail. I'm now led to believe my GPU is on its way out. Guess that's as good a time to upgrade as any!