Uploading a New Route

I am trying to upload a new route but each time it fails when I select the gpx file.  I get a new window with just ‘Error 500’ above a black rectangle every time.  The gpx file was created using a third party app Outdooractive with the start and end co-ordinates changed to those of the meeting points at either end.  Examining the gpx doesn't show anything out of the ordinary; it's just a regular xhtml file.

I've seen an older post where the problem was the OSmaps app this was fixed a long time ago.

Anybody got any ideas?