CiviMobile "unknown error" on Wordpress
There is the current situation with CiviMobile app and WordPress:


New CiviMobileAPI extension(https://civicrm.org/extensions/civimobileapi) is platform independent and works for all CMS Drupal/Joomla/WP.    
But, there is an issue in standard CiviCRM API for WP. This issue prevents our extension to use API properly.  
We proposed a quick fix for this problem. Our fix was rejected by the Core Team. And they started wider discussion in few threads. Please start reading here https://github.com/civicrm/civicrm-core/pull/12813#issuecomment-428152827


As now, we are still working on quick API patch for WP. I hope it will be available in the next few days. I will let you know as soon as it is ready.

As a long-term solution, we need a permanent fix which will be approved by the Core Team and included into standard CiviCRM code (see the issue above).

Thank you,
 Sergiy