Error message indicates that the Allocable Expense statement explanation is required to show that foreign taxes paid are definitely related to foreign income. This is related to a Schedule K-1 fiduciary beneficiary form.
Expert JulieS wrote the following regarding the Allocable Expense Statement explanation required for Form 1116 as shown on this link:
Yes, you will need to find out what you entered for "expenses definitely related to the income on line 1a" and "deductions not definitely related" first as these are data entry fields.
Here's how to find out what was entered:
If you didn't find any deductions while reviewing this section, but the request for an explanation comes up again in review, enter NA.