AMP doesn’t have any CurseForge integrations atm, it pulls from FTB’s site.
You could try these steps to clear the cache manually to see if that’s the issue:
https://discourse.cubecoders.com/t/direwolf20-1-21-update-issue/20602/4
AMP runs NeoForge fine, so you’ll want to double check that you’ve configured things right and have the Jar set to Autoselect.
And make sure that you’re not uploading a zip to the mods directory, as modloaders only load jar files.