Karoo 2 ride sync isn't working

My first ride today on my Karoo 2. I signed in and set up the device and loaded routes onto it via URL, had a successful ride and followed the routes. Maps were downloaded, suggesting WiFi is working.

Now when I want it to upload the ride to dashboard, it just sits there saying 'uploading'. It fails to appear in dashboard. Most recent attempt was still 'uploading' when I got back from half hour walk. multiple attempts. During one attempt, I loaded a new route onto the K2 and it transferred and appeared immediately.

Why might the ride not upload successfully? Major reason for the Karoo 2 was to upgrade from old computer that had to be plugged in to upload!

I've checked for system update and it says up to date, checked as of now

Update: I tried acquiring a second ride, for 10s and when I uploaded that it happened as expected and synced incl. to Suunto in seconds. This morning's file is still just hanging there 'uploading'. Perhaps I can interrogate the file manually? I've downloaded the .fit file, what can I do with that? The fit file seems complete because I uploaded it to Garmin Connect without issue.

Thanks