wifi transfer stuck on "transfer already in progress"

Garmin edge 840 on firmware version 26.18.
Garmin express for Mac on version 7.25.

I had a lot of trouble updating from version 24.x to 26.18 but eventually it worked with garmin express and a generous amount of troubleshooting with help from other users posts. Unfortunately I'm not able to update maps to 2024.20:
- garmin express doesn't find the update for the maps
- garmin edge finds the map update but says "transfer in progress - waiting for the current wifi transfer to finish". No clue about what is already transferring.
- garmin edge in "check for updates" submenu says "transfer already in progress" in a red circle. Again, no clue about what is already transferring.

Two questions:
- How can I find what is transferring (maps? firmware?)? It's been stuck on that popup for days.
- How can I update the map if even garmin express can't find them?

Thanks for your help.
Have a nice day