When I go to a CAA upload page in HTTPS I always see:

Warning: The Cover Art Archive is currently experiencing difficulties. Adding images for this release is unlikely to work at the moment.

⚠ Error uploading image

In HTTP, it's OK.

I eventually create a ticket because at first I thought it was because of some company firewall, but I have noticed the same at home.

Both PC are with Opera 12.17 on Windows XP and 7.

Maybe because of Opera 12.17? Maybe something has changed recently (I have this error for 1 or 2 months).