When you tried to place a Pipe or Pipe fittings in Message Center it is showing 'Catalog Items are not found'
There could be two solutions for this case,1. Go to the DataGroupCatalogs folder,C:\ProgramData\Bentley\OpenBuildings CONNECT Edition\Configuration\Datasets\Dataset_NM\DataGroupCatalogsAnd try to find related XML files. If that can not be found copy and paste those files from backup folders. Here is a video that will show the required steps,
2. If the backup folder of that DataSet was not stored please modify the DataSet so that the missing files will be downloaded again,