Why are product attributes not visible on some models?

There are two reasons why a product attribute may not be visible in some cases.

Attribute not defined for custom models

When a new attribute is defined it can be added to specific models

Catalog --> Product --> *Select model* --> Custom Options --> + ADD NEW ROWS

This will apply to all simple child products such as different sizes of the same model. However, the attribute is not automatically defined for the full custom model. That should be manually selected for each custom model you want the attribute to be applied to.

Catalog --> Product --> *Select model* --> Recommended Products --> *select edit on the full custom (first) row*

That will open a new window. Now select the custom options and select the attributes you would like to be available.

Custom Options --> PRICES

Wait a moment for the page to load all the possible custom options, this can take up to a minute.

Attribute is enabled only for some customers (for example, not visible on frontend website)

When an attribute is defined there is an option to set if that attribute is available for specific customer groups. It's possible that the attribute has been set as excluded for the customer viewing the product. Ensure the exclude check box is disabled (not ticked) for any customer groups you would like to be able to see this attribute.

Catalog --> Attributes --> *select attribute* --> Manage Label / Options --> PRICE/EXCLUDE

This can also be defined within the specific models

Catalog --> Product --> *Select model* --> Custom Options --> PRICES