Copy Rebis.cfg from C:\Program Files (x86)\Common Files\Bentley Shared\RealDWG2014\ to C:\Program Files (x86)\Bentley\ProStructures\V8i_S6\PowerProduct\ProStructures\config\appl
Open ProStructures application and make sure that the configuration variable
MS_HANDLER_LOAD has rebisElementHandler expansion and MS_REALDWG_APPS variable has rebisAdapter expansion.