I use Quicken Classic Deluxe for Windows, Version R67.10 HF4 (May, 2026).
My American Express accounts have not been updating for about 2 weeks.
Not having any problems downloading AMEX, you may want to reset the account.
My one AMEX Account has been and is updating properly, and I don't see any AMEX issues reported in the Alerts section so this may be some sort of "local to you" problem.
Are you receiving any sort of error messages, warnings, anything that might indicate what's causing the problem?