Your CA has totally expired and there is nothing which openvpn can do to help you fix this.
Without very detailed information, I doubt there is anything you can do but to visit (physically or virtually) each and every device.
Hind-sight tells me, you need a proper disaster recovery scenario and now that you have experience in disasters you can probably prepare for such in the future ..
If all else fails you can contact me privately: tincanteksup <at> gmail
