"Debugging and troubleshooting", "List of MyChat Client errors", "Error #0299".
 
Error

Error #0299: you specified a non-existent ID (XXX) of the common user group, or the personal group with such ID does not belong to you
 

Error description

When adding a user group for accessing Kanban project you specified incorrect numeric ID, or this ID is personal and does not belong to you.

 
Problem solution

If you work with MyChat via API or directly using an open network protocol, change the transferred data.