Can't Add units to course after upgrading theme to 2.x

<p class="p1"><span class="s1">Hi</span></p> <p class="p2">Since upgrading the theme to 2.x we can’t add units to a course anymore.</p> <p class="p1"><span class="s1">We have deactivated all plugins - except the core plugins which wont allow deactivation.</span></p> <p class="p1"><span class="s1">I as much as we can, we have tested for  JS errors</span></p> <p class="p1"><span class="s1">But the problem persists</span></p> <p class="p2">I will supply you with  our login details to resolve</p> <p class="p2"></p> <p class="p2">Thanks</p> <p class="p2"><span style="line-height: 1.5;">Brian</span></p>