And, indeed, there it may be! The problem may lie with the security protocols and ciphers specified in the cert: Security protocol TLS v1.2 128 bit AES GCM (256 bit ECDHE_ECDSA/SHA-256)
Breaking that down:
TLS v1.2 specifies the TLS (and its version) handshaking protocol, for establishing secure communications
128 bit AES GCM means the browser client will verify the key's validity using an AES 128-bit algorithm to communicate
ECDHE_ECDSA specifies the browser client and the server will agree on encryption keys using Ephemeral Elliptic Curve Diffie-Hellman with Elliptic Curve Digital Signal Algorithm for digital signatures
SHA-256 is the algorithm to be used for secure hashing of parts of the TLS messages
Unfortunately, Olde Opera versions don't list ECDHE_ECDSA (or any other ephemeral elliptic ciphers, for that matter) as available in the browser for usage in establishing https traffic pathways. Most newer browsers now include ephemeral elliptic ciphers in their cipher suites and many secure websites have moved on accordingly, but unfortunately, Olde Opera is locked in space and time at a point several years ago.