I went for a bike ride earlier today and all good with my vivosport. Just looked at the band and I have a Garmin icon in the display and not responding.
Have you tried connecting the device to a computer using the charging cable? This should get the device to go into mass storage mode and attempt to sync with Garmin Express. There may be a corrupted file on the device causing this behavior. If syncing with Garmin Express does not resolve the issue, please visit support.garmin.com as the device may need to be replaced.