Dear Greg,
I've followed the step-by-step instruction on https://github.com/jefferis/fiji-cmtk-gui 

to install the CMTK GUI plugin on a 10.15.7 Mac OS X  with clean installs of Fiji. I installed Fiji, downloaded the CMTK GUI zip, expanded it, renamed it to CMTK_Registration, moved it to the plugins/Scripts/Plugins folder, and restarted Fiji. While CMTK_Registration appeared in the Fiji Plugin menu [1] - image attached, clicking one of the options, such as "Install CMTK" or "Update to development CMTK  GUI" gave me this error message on the console [2].

[2]
[ERROR] Traceback (most recent call last):
File "Install_CMTK.py", line 11, in
ImportError: No module named cmtkgui

at org.python.core.Py.ImportError(Py.java:329)
at org.python.core.imp.import_first(imp.java:1230)
at org.python.core.imp.import_module_level(imp.java:1361)
at org.python.core.imp.importName(imp.java:1528)
at org.python.core.ImportFunction.__call__(__builtin__.java:1285)
at org.python.core.PyObject.__call__(PyObject.java:433)
at org.python.core.__builtin__.__import__(__builtin__.java:1232)
at org.python.core.imp.importOne(imp.java:1547)
at org.python.pycode._pyx1.f$0(Install_CMTK.py:81)
at org.python.pycode._pyx1.call_function(Install_CMTK.py)
at org.python.core.PyTableCode.call(PyTableCode.java:173)
at org.python.core.PyCode.call(PyCode.java:18)
at org.python.core.Py.runCode(Py.java:1687)
at org.python.core.__builtin__.eval(__builtin__.java:497)
at org.python.core.__builtin__.eval(__builtin__.java:501)
at org.python.util.PythonInterpreter.eval(PythonInterpreter.java:255)
at org.python.jsr223.PyScriptEngine.eval(PyScriptEngine.java:57)
at org.python.jsr223.PyScriptEngine.eval(PyScriptEngine.java:31)
at javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:264)
at org.scijava.script.ScriptModule.run(ScriptModule.java:157)
at org.scijava.module.ModuleRunner.run(ModuleRunner.java:165)
at org.scijava.module.ModuleRunner.call(ModuleRunner.java:124)
at org.scijava.module.ModuleRunner.call(ModuleRunner.java:63)
at org.scijava.thread.DefaultThreadService.lambda$wrap$2(DefaultThreadService.java:225)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)



I tried moving cmtkgui.py helper script out of the CMTK_registration folder as recommended by erichamc https://github.com/jefferis/fiji-cmtk-gui/issues/1. Restarted Fiji> Install CMTK. It doesn't seems to fix the problem.

Any other recommendation?

Caroline