More testing today. Went out to drive the van at 8:00am, unplugged the charger, climbed in and pressed the start button. Dashboard screen came on but the UConnect screen did not. Pressing the UConnect power button did nothing. Based on what I had read somewhere I turned the van off, opened the hood and pulled and reinserted fuse F76. Got back in pressed the start button again and the UConnect screen came alive this time. So a power reset of the UConnect system fixed that, at least temporarily.
Came back at 12:45 with an empty battery. Turned the van off, plugged in the charging cord and observed that it was waiting to charge (scheduled charge was set to 9pm). Now just to try something different I turned the van on,changed the charging schedule to start at 1pm then turned it off again. Observed that it was still waiting to charge, as it should. At 1pm, lo and behold, it started charging. Unplugged the charging cord, changed the schedule to start at 9pm again and plugged the charging cord back in. Observed that it was waiting to charge. We shall see what happens this evening.
So the correct startup of charging this afternoon could be because:
a) I did a power reset on the UConnect system earlier in the day
b) There was only 15 minutes elapsed between plugging in the charger and the next charging start time instead of the usual several hours.
c) There is something special about a schedule that starts at 1pm instead of 9pm
d) The behavior is totally random