It sounds like there may be an issue with the configuration of your inventory management system in Odoo. Without more information about your specific setup and the steps you are taking to create and reserve materials, it is difficult to provide a detailed solution.

However, here are a few things you can check to troubleshoot the issue:

1. Make sure that the "Make to Stock" option is enabled for the product you are trying to reserve. This can be found in the inventory settings under the "Inventory" tab in the product form.

2. Verify that the product is properly configured as a "Stockable Product" and that it is assigned to the correct location.

3. Check the availability of the product in the "Inventory" and "Planner" tabs under the "Inventory" menu to see if the reservation is being made correctly.

4. Confirm that the "Procurement" rules and "Inventory" settings are correctly configured for the product.

5. Make sure that the reservation is done in the planned section of odoo

Hello.
The product is indeed enabled with the attributes you mention, however the problem continues and not in all products.
In the Operations the product reservation is enabled the option Immediately after the confirmation of the sales order.

I don't know if it helps, but I'm using Odoo version 13 Community