I purchased lightroom 6 for my mcbook pro in june, installed it and used it once or twice just fine. (I also had a trail version of lightroom 5 and creative cloud installed separately before purchasing 6) I have not used the application for a few months, and have tried to open it this week without success, it launches the picture of the forest foliage and freezes. I uninstalled the lightroom 5 version, to no avail.
If you are using the trial of Creative cloud as well, please uninstall it from the computer and try to launch the Lightroom again.
Thank you. I did that and now lightroom opens, so I assume it is fixed now.