How in the world do I get files from my Edge540 to WKO5 after firmware 25.24???

After the most recent firmware, I am no longer able to mount my Edge540 on my Macbook, and no longer able to get files to my training software.

How can I work around this? If not, then how do I downgrade the firmware?

This is a complete dealbreaker for me! If there is no way around it, I will have to switch away from the 540.