Eacles imperialis

I have recently had two males and three females of Eacles imperialis emerge, lovely large specimens. Unfortunately, I cannot get them to pair - any suggestions please?

I have tried them outdoors in a cylindrical netting cage, both dry and sprayed with water and inside also without air movement.
Temperatures of between 65-75F have been normal.

I've also tried hand-pairing which has not been successful.

Any tips or ideas would be appreciated!