The SQL0444 is generated on an execute or execute direct when the database server is able to locate the procedure declaration but is unable to locate the program object.
The external program must be in the location specified in the system catalog tables. Note that this location is defined by the naming convention and default collection in affect when the procedure is defined (using CREATE PROCEDURE) and not when the procedure is called. To check the location defined for the external program name of a stored procedure run a query over QSYS2.SYSPROCS and note the value for the "EXTERNAL_NAME" name field.