Addin's disconnect and cannot be opened.

[toffypops]

I find myself really frustrated. 

1. I make an addon folder and work on the addon. I can set it to load on startup etc, and as long as I do not close fusion, it works fine. 
2. ...but often when i Start fusion the addon is not loaded, despite exit was clean and it was set to load on startup. 
3. When i try to open the folder from fusion I get this error when i try to open the folder where the addin was previously loaded from: 
   
   I know for a fact the addon works, because i can rename the original folder, then recreate addon in Fusion and then move and overwrite the files in the new addon folder with the files from the old. 
4. Then reload the addon and keep working on it.. 
5. And yes, names are identical both in the json/manifest, foldername,py-name,etc. So this error is incorrect in stating files do not exist. 
6. Then I log out and into fusion, and sometimes face the same problem again and have to rename and copy the folder. 

[KrisKaplan]

The normal rules to resolve a script|addin are as you mentioned. For Python, it is expected that files with the exact same name as the folder with the '.manifest' and '.py' extensions are found in that folder. The most common problem is when a script is copied such that the folder name now no longer matches the manifest and script files. (Which does not sound like your issue.)

But perhaps the next most common issue is that the .manifest file must be parse-able as a json file. If the manifest file fails to parse, it will fail to load, which will cause the script/addin to fail to load. (And creating a new addin goes through some different logic to be added to the list of scripts, so it may be more permissive in some ways.) Make sure the contents of your manifest is valid json.

Otherwise, you can look in the application event log for entries whose message starts with "API:". There are a couple more obscure issues that could cause these error logs to get written.

Kris