I had this exact same problem. Except my solution was to add an “s” to the binding value.
Old:
binding=”mexHttpBinding”
New:
binding=”mexHttpsBinding”
web.config snippet:
<services>
<service behaviorConfiguration="ServiceBehavior" name="LIMS.UI.Web.WCFServices.Accessioning.QuickDataEntryService">
<endpoint behaviorConfiguration="AspNetAjaxBehavior" binding="webHttpBinding" bindingConfiguration="webBinding"
contract="LIMS.UI.Web.WCFServices.Accessioning.QuickDataEntryService" />
<endpoint address="mex" binding="mexHttpsBinding" contract="IMetadataExchange" />
</service>