debugging tagging of duplicates - lefant/ng-flickrdupfinder GitHub Wiki
when clicking a thumbnail to mark as a duplicate the following should happen
- first the thumbnail is fully visible

- thumbnail turns 50% gray (request in progress)

- thumbnail turns 70% gray surrounded by a red line (request to add tag flickrdupfinder acknowledged by flickr api)

a screenshot of the javascript console / the network console just after clicking on a thumbnail to mark it as a duplicate is useful for debugging. there are good instructions on how to get them here:
https://en.support.wordpress.com/browser-issues/advanced-browser-troubleshooting/#javascript-errors
https://en.support.wordpress.com/browser-issues/advanced-browser-troubleshooting/#http-headers