Unable to Edit DFF field in Edit Invoice Screen through Form Personalization Sandbox

Summary:

Unable to Edit DFF Fields in EDIT INVOICE screen to extract the exact label name
Payables > Invoices > Manage Invoices > search with any of the Invoice number > Actions > edit.

When i enter into sandbox to edit that particular DFF, i am unable to edit options.

it seems to be disabled, we have tried by various setups enabling DFF Option still issue continues.

Can anybody help me in finding the issue, to edit particular DFF through Sandbox Form Personalization.

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