Error selecting pending invoices in Invoice Entry

Error selecting pending invoices in Invoice Entry. 

Program stopped at 'apinvent_pending.4gl', line number XXXX. FORMS statement error number -8092. At least one field for this INPUT ARRAY must be editable.

• Munis 
• Accounts Payable 
• Invoice Entry 

There are no updateable fields available

Munis > Financials > Accounts Payable > Invoice Processing > Invoice Entry 

1. Select Pending Invoices 
2. Right click on a column header. Example: Invoice Type 
3. Select a column that can be modified, such as Selected