Solibri is a specialized IFC software and uses all of the IFC data model, however, SYNCHRO Pro's data model is very different, and don't have defined relationships for all of the IFC object types. It can import IFC elements that are defined in IFC as "IFCPROPERTYSET", and some additional information that is hardcoded relations or objects which were requested (like IfcGUID, IfcType, IfcBulding, IfcBuildingStorey..)

If you can move the properties to a field that is included in IFCPROPERTYSET, then SYNCHRO Pro may be able to show those properties.