All of a sudden I have two issues with Thunderbird. First, when I go to my sent folder to try and open a PDF file attachment I sent someone, I get the message: Adobe Acrobat Reader could not open '[filename]-1.pdf' because it is either not a supported file type or because the file has been damaged (for example, it was sent as an email attachment and wasn't correctly decoded). This even happens when I try and send myself an email PDF attachment. My second issue that has just started is when I click on the file attachment in the email. It used to be that the file would just open and now it just saves it to the desktop and I have to click on it to open it. But then that brings me to my first issue in that I can't open the file due to the previously listed error message. I'm not sure what to do or how to troubleshoot. I've downloaded the latest version of Adobe Acrobat Reader and that didn't fix the problem. Both issues have just started within the last couple of days and out of the blue. I am using Mac OS 10.14.1. Any suggestions?