Salesforce Nonprofit Cloud: "You don't have permission to modify" error in Gift Entry despite granted field access

This article explains why a Nonprofit Cloud Fundraising user may receive a permission error when clicking the New or Edit Gift Entry button, or when running the Manage Gift Commitment Schedules invocable action, after you have already corrected field-level security.

Users see errors such as "You do not have permission to modify npe__Recurring_Donation__c/npe__Recurring_Donation_Campaign__c" or "[user] doesn't have access to [field]" where the message references fields like ObjectSourceCodeId or PaymentInstrumentId but does not state which object those fields belong to. The New and Edit buttons fail while the pencil-edit on an existing Gift Entry field may still work.

This affects non-administrator profiles and permission sets that have object-level Edit but incomplete field-level security across the full set of related Fundraising objects (GiftTransaction, GiftTransactionDesignation, GiftCommitment, GiftCommitmentSchedule, GiftSoftCredit, GiftDesignation).