Whilst working in Lr 6 it froze when I tried to load an image into Develop. Only way I know was to press escape. Now when I try to start Lr a dialogue box tells me to close the running version of Lr. How do I do it?
Open the folder that contains your Lightroom catalog and look for a file with the same name as your catalog, but with the .lock extension. That lock file needs to be deleted and then Lightroom will start again. This is a file created by the underlying database technology. It is normally deleted when Lightroom closes normally. When there are problems that file can be left behind. It has to be deleted manually. It is the only file you should delete.