Why Can I only use budget year number multi period tab of Budgetary Control Budget Import template?

When using the budget import FBDI template multi period tab and entering budget year (eg.2026) in the "Budget Year or Budget Year Number" field the import always ends in warning without identifying the previously uploaded template zip file. When I change the budget year to a budget year number (eg.1) the upload succeeds. The client needs to be able to use the budget year.

Budget calendar details = budgetary control only.

Period Frequency = Other

Number of Periods = 4