I had the same thing some weeks ago.
Transfer somehow didn‘t see syx but the newer filetypes and strangely os upgrade ( also syx).
(Can‘t remember if it worked with a previous version as i mostly used c6 (pc) and not often)
Same thing with dn with mac and a4 with pc…
I had to use sysex librarian for mac.
Search for the program and read dn manual sysex dump.
I replied some days ago somewhere else, one person was able to send sounds (but not banks) with first clicking sysex transfer below on transfer. I didn‘t try that.
I hope its ok if i have mix of syx and new filetypes sabed as backup(?)