Garmin Edge 520 = Course file

[Block]

When uploading a course to my Edge 520 from the Androud App or Garmin Connect the file shows on the device. However when trying to open the file I get the message "Invalid file. DELETE." Also shows same result on older courses that previously worked 100%.

Followed same procedure on Wife's Edge and work 100%.

Any advice on how to fix it.

Saw on Garmin forum a lot of similar queries but no solution.