I recommend using the RHS site for seeing if a cross is registered (although you do have to check the cross in both directions [EG: rex × grandis and grandis × rex]). Another place I use a lot is https://bluenanta.com/.
I still have trouble sometimes using the RHS orchid database heheheh. I have a feeling that data-base needs an upgrade. Or could have improved features. But better than nothing, that's for sure!