W10, all updates, Thunderbird email.

Until today, I was able to open attachments, simply by clicking on them.

Today, when I click on one, it asked me to save it, which I did, but I don't know where it went. I get a list of downloads, and other files. If I click on one, it tells me it already exists. What have I messed up. I just want to open it, by just clicking on it, as I did before.