I'm having trouble getting this to work

[Deltron216]

When I try to install via the "Load Plugin From File" utility in Calibre I get the following error:

calibre, version 2.21.0
ERROR: Unhandled exception: InvalidPlugin:The plugin in u'D:/Downloads/Chrome/isfdb-calibre-master/isfdb-calibre-master/isfdb-plugin.zip' is invalid. It does not contain a top-level init.py file

calibre 2.21 isfrozen: True is64bit: False
Windows-8-6.2.9200 Windows ('32bit', 'WindowsPE')
32bit process running on 64bit windows
('Windows', '8', '6.2.9200')
Python 2.7.9
Windows: ('8', '6.2.9200', '', 'Multiprocessor Free')
Successfully initialized third party plugins: Extract ISBN && Goodreads && Comicvine && Goodreads Sync && Find Duplicates
Traceback (most recent call last):
File "site-packages\calibre\gui2\preferences\plugins.py", line 316, in add_plugin
File "site-packages\calibre\customize\ui.py", line 388, in add_plugin
File "site-packages\calibre\customize\ui.py", line 53, in load_plugin
File "site-packages\calibre\customize\zipplugin.py", line 188, in load
File "site-packages\calibre\customize\zipplugin.py", line 286, in _locate_code
InvalidPlugin: The plugin in u'D:/Downloads/Chrome/isfdb-calibre-master/isfdb-calibre-master/isfdb-plugin.zip' is invalid. It does not contain a top-level init.py file

When I open the Zip, it's in there, so I'm not sure what's going on

any help would be appreciated.