Had this problem today (system: Ubuntu on PC (Firefox), Ubuntu Phone (built-in no-name browser)).
Importing the lesson works smoothly (line breaks missing as a known bug, of course), but I cannot create a fresh course to add the lesson to.
I insert the course name, press ‘save’ and this message comes up:
"
Field “completed_count”: This field is required.
"
There is no such field…
Please help!
I will check later if I see the same behaviour under windows (7).
I am experiencing the same (macbook, all browsers: Safari, Opera, Chrome, Brave). I can create lessons, but not new courses.
Same problem too.
Sorry about that everyone! We will get that fixed asap!
Thank you 
I am experiencing the same problem
I am getting this issue too. I can’t create a course or even add lessons to a course.
I just get this message every time. Very frustrating.
Please correct the following errors:
Field “collection”: Select a valid choice. 347282 is not one of the available choices.
This issue should be fixed now. Thanks again for reporting the issue and helping us to fix it.
I am still getting the same problem. I am trying to create a course by adding a lesson to one I uploaded yesterday. But its coming back with the same error;
Please correct the following errors:
Field “collection”: Select a valid choice. 347282 is not one of the available choices.
Strange, can you contact us on support(at)lingq.com and send us link to that lesson, and also link of the course in which you are trying to add a lesson. Thanks!
Thanks, email sent.
In my case it’s fixed alright Thanks a lot!