We have upgraded our SEPHP to V6 and then upgraded all the plugins. The directory/pages plugin is installed without a problem but when I click on "Pages" link (the link that should show me the page items and categories), it gives the following error: "We are currently experiencing some technical issues. Please try again later. Error code: 78c991"  (The error code is random and changes every time).

This error is not logged in SE error log. Also it is not logged in Cpanel error log. We cannot find the source of this error and we are exhausted.

It would be very appreciated if you you guide me on this.

Contact SEA.
We had the problem too and they intervened quickly.