Actually, the Yuasa battery failed before the starting problem began. Everything had been working normally, and one day I attempted to fire it up. Turned on the key and there was no display. I checked battery voltage but apparently there was an internal problem. The tech at the dealer said this was common. The battery was under warrantee, but to get it replaced I needed to get the rig to the dealer, have the battery charged overnight, and the bike systems checked. For me, that would have been an overnight stay, so it was cheaper to buy a new battery. I bought an Optima, installed it, and everything powered up normally.
Then, with an important trip departure, I attempted to start it and it wouldn't. Got the display, clicked the M selector, and nada. I momentarily thought about loading all the gear in the old airhead sidecar rig, but tried it one more time and it started. But at the first rest stop it wouldn't start.
I've completed the initial service, and have tried some experiments. The tech mentioned that the mode switch is problematic, using a magnet that apparently slips out of position. I'll be taking the Spyder to the dealer next week for some diagnostics. I'll drop it off and let them play with it for as long as needed.
One test was to unplug the brake low pressure switch and see if it would start normally. It just reported a brake failure.
I can still get it to start by pressing the M switch and releasing it multiple times with the starter switch held in. Eventually it will start. And once it has started, it will start normally within a few seconds. If the scrolling display message reappears, it won't start.
I'm suspicious that the failed battery may have caused a computer fault.
As a strange turn of events, when I attempted to hitch up the trailer to load up the Spyder for the trip to the dealer, my Toyota battery was dead. I hauled it to the dealer in the sidecar rig, bought a new one, and returned with the 4Runner for a service. They mentioned that this would be the serious 90,000 mile "replace everything" service. They didn't finish it today, so I guess I'll have to wait until next week to transport the Syder to the dealer (about 3 hours away)