American Express is discontinuing the upgrade with points program starting December 3, 2023. On statements the following is stated:
Effective December 3, 2023, American Express Card Members with a Membership Rewards account will no longer have access to the Upgrade with Points program and, accordingly, will not have the option to use Membership Rewards points to place an offer on a seat upgrade for any upcoming flights. This will not impact offers placed for a seat upgrade prior to December 3, 2023. All pending offers will still be processed and accepted or declined by the airline. This will not impact any offers that, as of December 3, 2023, have already been accepted or declined by the airline. Upgraded tickets for accepted offers will continue to be valid.
Not a huge loss given how bad value this program was but something to be aware of.
Hat tip to HappyP2