matplotlibwidget Install issue - python-2.7

Question

I have a strange problem. I am using a program developed in python 2.7 (not by me). The software use matplotlib and I installed it fine. But somehow I still get this error. Anyone has any idea what to check?
Traceback (most recent call last):
File "C:\Daten\R&D\Labor\pyLogger_RS485\GUI_MasterLogger.py", line 460, in <module>
mainwindow = MainWindow()
File "C:\Daten\R&D\Labor\pyLogger_RS485\GUI_MasterLogger.py", line 26, in __init__
self.initUI()
File "C:\Daten\R&D\Labor\pyLogger_RS485\GUI_MasterLogger.py", line 56, in initUI
self.ui = uic.loadUi('uiGUI_TCCO2_MasterLogger.ui')
File "C:\Python27\lib\site-packages\PyQt4\uic\__init__.py", line 238, in loadUi
return DynamicUILoader(package).loadUi(uifile, baseinstance, resource_suffix)
File "C:\Python27\lib\site-packages\PyQt4\uic\Loader\loader.py", line 71, in loadUi
return self.parse(filename, resource_suffix, basedir)
File "C:\Python27\lib\site-packages\PyQt4\uic\uiparser.py", line 951, in parse
actor(elem)
File "C:\Python27\lib\site-packages\PyQt4\uic\uiparser.py", line 790, in createUserInterface
self.traverseWidgetTree(elem)
File "C:\Python27\lib\site-packages\PyQt4\uic\uiparser.py", line 768, in traverseWidgetTree
handler(self, child)
File "C:\Python27\lib\site-packages\PyQt4\uic\uiparser.py", line 242, in createWidget
self.traverseWidgetTree(elem)
File "C:\Python27\lib\site-packages\PyQt4\uic\uiparser.py", line 768, in traverseWidgetTree
handler(self, child)
File "C:\Python27\lib\site-packages\PyQt4\uic\uiparser.py", line 242, in createWidget
self.traverseWidgetTree(elem)
File "C:\Python27\lib\site-packages\PyQt4\uic\uiparser.py", line 768, in traverseWidgetTree
handler(self, child)
File "C:\Python27\lib\site-packages\PyQt4\uic\uiparser.py", line 242, in createWidget
self.traverseWidgetTree(elem)
File "C:\Python27\lib\site-packages\PyQt4\uic\uiparser.py", line 768, in traverseWidgetTree
handler(self, child)
File "C:\Python27\lib\site-packages\PyQt4\uic\uiparser.py", line 233, in createWidget
self.stack.push(self.setupObject(widget_class, parent, elem))
File "C:\Python27\lib\site-packages\PyQt4\uic\uiparser.py", line 194, in setupObject
obj = self.factory.createQObject(clsname, name, args, is_attribute)
File "C:\Python27\lib\site-packages\PyQt4\uic\objcreator.py", line 106, in createQObject
factory = self.findQObjectType(classname)
File "C:\Python27\lib\site-packages\PyQt4\uic\objcreator.py", line 131, in findQObjectType
w = module.search(classname)
File "C:\Python27\lib\site-packages\PyQt4\uic\Loader\qobjectcreator.py", line 107, in search
module = __import__(mname, {}, {}, (cls,))
ImportError: No module named matplotlibwidget
Thanks in advance,
Umberto