freenas 11 - unable to update pms from 1.10.1 - 1.12.1



hi, im new to freenas - im only using it for pms - i first install from freenas 11 plug's list and configured it and working fine. but there was an update and it will not install.

i get an error message

the file is (PlexMediaServer-
this file update is currently to date not in freenas plugins page

the error message is -

" Environment:

Software Version: FreeNAS-11.1-U4 (89e3d93bc)
Request Method: POST
Request URL:

File "/usr/local/lib/python3.6/site-packages/django/core/handlers/" in inner
42. response = get_response(request)
File "/usr/local/lib/python3.6/site-packages/django/core/handlers/" in _legacy_get_response
249. response = self._get_response(request)
File "/usr/local/lib/python3.6/site-packages/django/core/handlers/" in _get_response
178. response = middleware_method(request, callback, callback_args, callback_kwargs)
File "./freenasUI/freeadmin/" in process_view
162. return login_required(view_func)(request, *view_args, **view_kwargs)
File "/usr/local/lib/python3.6/site-packages/django/contrib/auth/" in _wrapped_view
23. return view_func(request, *args, **kwargs)
File "./freenasUI/plugins/" in upload_nojail
497. return upload(request)
File "./freenasUI/plugins/" in upload
472. form.done()
File "./freenasUI/plugins/" in done
143. if notifier().install_pbi(pjail, newplugin):
File "./freenasUI/middleware/" in install_pbi
1814. "This file was not identified as in PBI "

Exception Type: MiddlewareError at /plugins/plugin/upload/
Exception Value: [MiddlewareError: This file was not identified as in PBI format, it might as well be corrupt.] "

please can anyone help me