Ho risolto, il primo era una dimenticanza mia, mancava il datasource del report:

codice:
cryRpt.SetDataSource(_data.Tables[0]);
poi ho impostato il tableinfo cosi:

codice:
CrystalDecisions.Shared.ConnectionInfo crDbConnection = new CrystalDecisions.Shared.ConnectionInfo(); 
crDbConnection.IntegratedSecurity = true; 
crDbConnection.DatabaseName = "FacileSagra.accdb";
 crDbConnection.ServerName = Global.getDbPos ; CrystalDecisions.CrystalReports.Engine.Database crDatabase = cryRpt.Database; CrystalDecisions.Shared.TableLogOnInfo oCrTableLoginInfo;
 foreach (CrystalDecisions.CrystalReports.Engine.Table oCrTable in crDatabase.Tables) 
{ 
oCrTableLoginInfo = oCrTable.LogOnInfo;
 oCrTableLoginInfo.ConnectionInfo = crDbConnection; 
oCrTable.ApplyLogOnInfo(oCrTableLoginInfo);
 }
e funziona