Upgraded site from 5.0.8 to 5.1 and now I can't add content

Plone Support
3

Do you have some older addons installed? If your addons require formlib and CMFDefault the issue might be

Try solving it like this https://docs.plone.org/develop/addons/upgrade_to_51.html#cmfdefault-removal
I did not test if that works, I still have a meta.zcml in my project with:

<configure
    xmlns="http://namespaces.zope.org/zope"
    xmlns:zcml="http://namespaces.zope.org/zcml">

  <configure zcml:condition="installed Products.CMFDefault">
      <exclude package="Products.CMFDefault.browser" file="configure.zcml" />
      <exclude package="Products.CMFDefault.formlib" file="configure.zcml" />
      <exclude package="Products.CMFDefault.upgrade" file="configure.zcml" />
  </configure>

</configure>