Created a simple customization to add Principal employee and PO number to a project in 23R2, customization work without any issue until upgrade.
After upgrade in Sandbox, there is an error message.
\App_RuntimeCode\PX_Objects_CT_Contract_extensions.cs(35): error CS0246: The type or namespace name 'EPEmployee' could not be found (are you missing a using directive or an assembly reference?)
I have come at this several different ways, and just create new error messages. I feel that I am missing something very obvious.