Can you show me the output of the text commands window @poetro0? You can access this by going to File > View > Show Text Commands

**Here it is. I stopped and reran it **

===== Error =====
run
Traceback (most recent call last):
File "C:/Users/pietr/Downloads/Fusion-Exporter-0.1.0/FusionExporter.py", line 7, in run
entry.start()
File "C:\Users/pietr/Downloads/Fusion-Exporter-0.1.0\commands\entry.py", line 28, in start
cmd_def = ui.commandDefinitions.addButtonDefinition(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users/pietr/AppData/Local/Autodesk/webdeploy/production/2f98b3925294fb88cbae05383e953941ed5106e7/Api/Python/packages\adsk\core.py", line 6330, in addButtonDefinition
return _core.CommandDefinitions_addButtonDefinition(self, *args)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeError: 3 : invalid id

===== Error =====
run
Traceback (most recent call last):
File "C:/Users/pietr/Downloads/Fusion-Exporter-0.1.0/FusionExporter.py", line 7, in run
entry.start()
File "C:\Users/pietr/Downloads/Fusion-Exporter-0.1.0\commands\entry.py", line 28, in start
cmd_def = ui.commandDefinitions.addButtonDefinition(
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users/pietr/AppData/Local/Autodesk/webdeploy/production/2f98b3925294fb88cbae05383e953941ed5106e7/Api/Python/packages\adsk\core.py", line 6330, in addButtonDefinition
return _core.CommandDefinitions_addButtonDefinition(self, *args)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
RuntimeError: 3 : invalid id

Managed to reproduce the error. It should be fixed now in the latest release @poetro0. Thanks for bringing it to my attention!