Make sure your addon details fill the requirements.

    # addons must fill this dictionary
    addonInfo = { 'id' : 'com.bondware.addon', # set this to a unique ID
    'author' : 'Bondware, Inc', # author info
    'copyright' : '(c) 2019 Bondware, Inc',
    'name' : 'MyAddOn', # this is the name of your plugin that will be visible in the GUI
    'version' : '1.1',
    'observer' : 0, # set to 1 if your addon implements the methods from SceneObserver
    'scenedata' : 0, # set to 1 if your addon implements the methods from SceneDataSaver
    'prefsdata' : 0, # set to 1 if your addon implements the methods from PrefsSaver
 #   'apiversion' : '1.0' # set this to the version of the addon API your addon is built for
        # this defaults to 1.0 so that older scripts that did not set this field will run in 1.0 mode
        # make sure to set this to the current version in your addon!
     }

ensure your addon is in a poser library which is loaded on startup. Edit the poser startup file by adding the following lines:

myAddonPath = os.path.join(os.path.dirname(poser.AppLocation()), "Runtime", "Python", "PoserScripts", "myaddon", "myaddon.py")
try:
    poser.ExecFile(myAddonPath)
except:
    pass

the following is adapted from Snarlygribbly's AVFIX

IMPORTANT: The installation requires you to make changes in the Runtime within the folder in which you installed Poser.
Depending upon your operating system, and where you have installed Poser, you may need to perform these steps with Administrator privileges.

STEP 1
    
    1.0 Create a folder called myFolder in the Runtime/Python/poserScripts folder ( this can also be Runtime/Python/poserScripts/ScriptsMenu ) 
    1.1 Copy  myFile.py file into myFolder

    When you have done this you should have this file in your runtime:
    Poser SoftwarePoser 11RuntimePythonposerScriptsmyFoldermyFile.py

STEP 2 (OPTIONAL)
    

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