By “the folder” do you mean inside the
Fiji.app folder? The location of the
ij.jar file should be in
Fiji.app/jars, and it will probably be called
ij-1.50e.jar (the error message leaves out the version number).
I just downloaded a Win-64 Fiji, and it looks like the
ij-1.50e is there. So if your installation is missing that file, it sounds like something interfered with your download or the extraction process.
If your file is in the
Fiji.app/jars folder, ImageJ may not be looking in the right place. Did the error message include any indication of where it was looking? If not, you can try running:
from the command prompt. If you could paste that information here we can see if it helps diagnose what went wrong.
Good to know. Did you try updating the lifeline version to the latest with
Help > Update...?
Thanks for the report and follow-up!