I downloaded lightroom 2015 in sept 2016. It worked for 2 weeks, now it won't even start.
It says I have the app already open.
It doesn't work with Win10 according to sales rep so they told me to come here if I needed help.
Is there a patch now so it does work? Are they working on a patch or am I out $150?
From your description, it would seem that you need to open the folder that contains your catalog and look for a file with the extension .lock. If you find such a file you need to delete it, and then Lightroom should start. Normally this lock file is deleted automatically when Lightroom closes. But if Lightroom did not close normally that file can sometimes get left behind. Give that a try and then report back..