We say this all the time on the streams.
It is an issue with Twitch.
The twitch missions, twitch containers and the Twitch prime drops are all different.
So you could get containers and not the mission.
The fix for this, is to unlink your account and relink your account if you have not yet gotten the mission and watched for the appropriate time. If this is still not dropping for you, please put a ticket in and let them know what all you have done.
Hopefully they straightened out the issue with your specific account.