The error message shows up when Takeoff is run. Alternatively not all objects in the drawing is included in the report.
First, make sure you have a QTO-file set in QTO Manager. These are per default stored in: C:\ProgramData\Autodesk\C3D <version>\enu\Data\Pay Item Data\<language>
If the error message is still displayed, your objects most likely doesn't have pay item assigned. For all objects except Corridors, you can use Edit Pay Items on Specified object to check, and add Pay Item to the object.
Pipe Network objects can have their Pay Item information added in the Parts list before the objects are placed.
For Corridors, the Pay Item information comes from the Code Set Style used. All Link Names and Point Names in a Code Set Style can have an attached Pay Item. When that Code Set Style is applied to the corridor, those Links/Areas and Points/Lengths can then be tallied. If the error message is displayed when a corridor is used, it either means the wrong Code Set Style is used on the corridor - or the Code Set Style doesn't include the correct links orpoints and/or Pay Item Information.