Update: Tried again, created a flat .zip file with all the .ovpn files. Note that the certificates are all inside the .ovpn files from my VPN vendor(NordVPN), there’s no additional file with the certificate.

E.g.

sleipnir (10:38) 342/0 $ zipinfo nordvpn.zip | head
Archive: nordvpn.zip
Zip file size: 20819055 bytes, number of entries: 9703
-rw-rw-rw- 3.0 unx 2808 tx defN 18-Sep-11 07:50 al10.nordvpn.com.tcp443.ovpn
-rw-rw-rw- 3.0 unx 2797 tx defN 18-Sep-11 07:50 al10.nordvpn.com.udp1194.ovpn
-rw-rw-rw- 3.0 unx 2722 tx defN 18-Jun-04 06:41 al4.nordvpn.com.tcp443.ovpn
-rw-rw-rw- 3.0 unx 2747 tx defN 18-Jun-04 06:41 al4.nordvpn.com.udp1194.ovpn

I see the files being unpacked into /tmp/ovpn_upload on the 750S, but I always get the dialog saying to “Please try again!”.