@era043 Unfortunately, I can't find a similar setting in Opera - if anyone knows of such a setting, it sure seems like that would be the answer!
I found the setting in Opera and it seems to fix the problem.
Settings > Advanced > Privacy and Security > Site Settings > Automatic Downloads.
I found that there was a block for Gmail. I turned on "Ask when a site tries to download ...." and the block disappeared.
It now works.! Thanks, @tomcha!