Answer
Yes — custom fields aren't universally available everywhere; R&D enforces custom-field restrictions on certain Logical Units or specific pages due to underlying design limitations, and these restrictions block custom fields from working at all on the affected screen regardless of how correctly they're configured. Project Analysis (built on the ProjectBalance LU) is one confirmed example, restricted at the LU level from a specific bug fix delivered in App10 UPD9 onward — on a page with this kind of restriction, only Custom Menus remain available as a customization option, not custom fields. If a custom field comes up blank across every approach tried, it's worth checking whether the specific LU/page is a known restricted case before continuing to debug the field's own configuration.