first things first, what version of Moodle and TaskChain are you using?
Also, please set Moodle debugging to DEVELOPER, and copy and paste the full debug message which shows at which line of which script the error occurred, in the same way the Deborah has done in this post.
If you try to create a "File" resource in the same section of the course where you tried to create the TaskChain, what happens?
If you try to create a TaskChain activity in the top section of the course, the "Intro" or "General" section that is never hidden, what happens?
Are you able to create your TaskChain on my test server without any errors?
- URL: http://bateson.kanazawa-gu.ac.jp/26/
- Course: Course Fullname 101
- Username: guestteacher
- Password: taskchainv09