Hello,
I was browsing through PPDS optimizer profile for thing and noticed there was a setting in the Resource Processing tab right at the bottom for container resource, please check if you have maintained the tick mark Consider Storage Properties.
(IMG>APO>supply chain planning>PPDS>PPT>maintain optimization profile)
F1 help says:
Considering Storage Properties During Optimization
If you set this indicator, the system activates container planning. Optimization then considers container resources regarding the maximum fill level and the settings for product purity according to the resource master data.
Best of luck!
Regards,
Abhishek