In reply to mbh:
master reset thing worked - thanks forthat.
And now, another thing. I can't get my Instagram pictures to appear on Strava. I use my Garmin 410 to record the run, which I upload OK to Strava, and the Instagram app on my iphone 5 to take the pictures during the run. These come up on my Instagram, but not on Strava. This has happened a few times now. When upload the run to Strava, it says for a while that it is syncing my pictures, but nothing appears, and then it stops saying that. It was only the first run where I tried this that my picture came up on Strava. Since then it has not worked. On that first run, though, I think I used the iphone to record the run too (becuase the watch was playing up - see above!). Since then, I have always used the watch.
I have connected my Strava account to Instagram, so far as I can tell, I have made my Instagram as public as I can see how (but maybe I am missing something, and I have written to Strava to ask them what I should do, who were very helpful (they are really good at writing back) but who can only suggest what I think I have already done. I have done all the dumb turn off- turn on, disconnect-reconnect things I can think of.
Any suggestions anyone? Does this happen to anyone else? Do I need to be recording the run too with the iphone Strava app, rather than with the watch? I can't find anything on the Strava site that says I do.