I cannot find "inventory" to add inventory items.

Thanks for reaching out to us here in the Intuit Community, @JanJaw.

May I know which specific option to enable inventory is grayed out? I'd appreciate if you'll get back with a screenshot so I can provide the correct information you need.

In the meantime, if you're referring to the Enable button under the Enhanced Inventory Receiving section, make sure to put a check mark beside Inventory and purchases orders are active on the Purchase Orders and Inventory section. This will give you the option to enable the feature.

I'll keep my eyes on this for your response. Thank you and take care always.