Not on Upgrade List until Activated by Agent?
 

What does that mean?

The upgrade list for my flight shows
Your name will not appear on the Standby list until
you are activated by the gate agent
This list is shown in order of upgrade/standby priority. Your Position on this list may change, based on determining factors such as frequent flyer elite status, fare type and delayed/cancelled flights impacting other passengers.

This sounds like you've waitlisted a GUC/RUC that hasn't cleared by T-24. Is this correct?

Nope, just a regular upgrade. Not a PM yet not until after this flight so no GUC or RUC for me.

This seems strange for a free elite upgrade (presumably to FC?) on a normal domestic flight. Can we assume that you're confirmed and ticketed correctly on the flight? Also, have you checked in?

The "activated by DL agent at the airport" is normally the GUC procedure. IIRC there have been reports (preCOVID-19) here of people missing upgrades because they weren't activated on time.

I checked in like an hour ago and have a boarding pass.

Is this a non-stop or a flight involving connecting segments?

Non stop JFK to SDQ at 1:35pm

My suggestion is to try the check-in transaction again. Whether you checked in first using the app or the web site, try starting the check-in process again using the DL.com website.

I tried checking in again says the same thing, waiting 4+ hours already for a call back from Delta.

Well while waiting for delta to call back I just checked again now it's showing on the Upgrade List probably a lag in the system. It shows me number one of 3 for 1 seat. so hopefully I get it

I had this for the first time last week, and no idea why. (One leg had already cleared to F, other hadn't cleared Y+). Didn't resolve after a few hours, so called. agent on the phone didn't know what happened and was able to manually add me to the upgrade list.

When you checkin if previously requested,you should automatically be added. From what I was told (no clue if true, but squares with experience) the airport upgrade list is separate from the normal processing. Thus why don't show on it till checkin. However this list should only be used at gate between 0-3 hrs prior to departure. Before that the automated processes should be handling the upgrades.

Why it's done this way? No idea.

I encountered this before. I flew from ORD to BOS with an award ticket and I was a gold medallian. At T-72 I was upgraded to C+ but at T24 I was not on the upgrade list after checking in. Called GM desk and they could not solve that and I had to activate at the gate. At around T2 I got to the gate, the gate agent could not handle this by herself. After about 1h of call, finally, I was on the list. She said the reason was that I confirmed the C+ upgrade, which I didn't.

Having the same issue today. Not appearing on the upgrade list for my JFK-SEA leg tomorrow morning, even though I requested an upgrade and I've already gotten my complementary to F on my second leg (SEA-GEG).

I see that Delta isn't helping customers through Twitter again, by the way. So much for trying to go the most passive route to get this fixed.

Try using the DL.com web site (not the app) and run through the "Check in for your flight" flow again.