Premiere Export Problems-Media Offline, and Unable to Open Export Window (Multiple Machines)

Finding two separate but equally confounding & infuriating issues with Premiere. 

Issue #1: I have my sequence ready to export, everything looks perfect. When I send to Media Encoder, the file shows that one of my video files is offline, despite it being online and playing back perfectly in Premiere. This happened on different machines at the same time. The only way I was able to export was to select "Replace Footage" and replaced the clip WITH THE EXACT SAME FILE, and even then I would only be able to export out of Premiere, Encoder still showed the file as offline.

Issue #2: On a different computer later in the day (different project file), not only was this happening, but Premiere wasn't allowing my editor to even open the "Export" window when he clicked on it in his project. When he tried to select "Export" by going through the File > Media menu, nothing would happen. The only way he could do this was through Media Encoder, which was showing his file as offline, even though the footage was on his desktop. 

During Issue #2 we saw that within 30 minutes of this issue starting Adobe released an available update to Premiere containing "important fixes" and we updated Premiere, and this issue was not fixed. 

Help!!!