We have a CiviCRM 5.15.0 installation under WordPress 4.9.10 and 2 MySQL db: one for Wordpress data and one for CiviCRM data. We manage more than 6500 contacts.

Going inside a contact we have this error message with a blank popup adding a meeting or phone call in the contact summary:

Network Error Unable to reach the server. Please refresh this page in your browser and try again.

There are NO ERRORS adding contributions, registering for events, adding pledges, sending emails.

Analyzing logs we have no errors on Apache, but we found a

CRM_Core_Error::backtrace("backTrace", TRUE)



last file

You can see how the errors come out on this video https://youtu.be/lrMq6A2t9Uk

  • If you haven't already, try admin - system settings - cleanup caches. If that doesn't help then open the browser developer tools and on the network tab or console tab try to see where it is failing when you create the meeting.
    – Demerit
    Jul 6, 2019 at 22:19
  • I did cleanup without changes. Here is the screenshot opening the browser developer tools and looking at the network tab picture Jul 7, 2019 at 9:55
  • Try opening the form in a new tab. Right click on the link and open in a new tab. Check CiviCRM Config Log to find more details of the error. Jul 7, 2019 at 10:18
  • I did it. here is the screenshot and here is the config-log last entry Jul 7, 2019 at 14:59

1 Answer 1


You have custom plugin or extension that is interacting with Activity type which expects custom fields in the system and is either disabled or deleted.

Solution: 1. Turn off the extension if the system no longer needs it. 2. Enable/Add the custom field or custom group back into the system



  • We tried to disable all the pluging one by one and in logical group with no changes. Is there a way to find the custom field/group name? Jul 9, 2019 at 13:58
  • 1
    Enable backtrace by navigating to Administer >> System Settings >> Debugging and Error Handling. And then reload the error page Jul 9, 2019 at 14:25
  • Sorry for the huge delay. Doing what you told me appears: CiviCRM_API3_Exception: "Expected one CustomGroup but found 0" with many more rows reporting about form contruction. Sep 21, 2020 at 10:25

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