Some interesting new info:

1) The following appeared on my Delta.com Trip Details page:

"Beginning with travel departing May 16, 2016, Delta Comfort+™ will appear as an option for booking along with Main Cabin and First Class on select flights. Complimentary upgrades to Delta Comfort+™ are still available for eligible customers. To ensure that you are placed in the queue for a complimentary Delta Comfort+™ or First Class upgrade, please check the box(es) in the Request Upgrade section below." (my emphasis added)

2) When I viewed the "Manage Upgrades" section, there was no mention of being in queue for an upgrade to First Class and there was no place to request one.

3) A call to DM line led to a complete revision of my PNR--new record locator ...that NOW correctly shows a) I've been "upgraded" to C+ (even though I was there from booking), and b) "Upgrade Requested for First/Business Class" shows for all segments.

According to Rep: Seems there was a "technical glitch" affecting this record. It's unclear if this is because I booked well before May 16 and travel starts on (or after) May 16.

Nice job by the representative...it took about 30 minutes and he called me back to confirm resolution.

Check your reservations.