The character count for the cover or steps may have exceeded the limit.
If the character count exceeds the limit, you can save a draft, but cannot publish. Please check the following and try publishing again:
Check the character count
If the character count for the cover or steps exceeds the limit displayed in the edit screen, please adjust the content.
Related articles:
What is the character limit for titles and descriptions?
https://help.teachme.jp/hc/ja/articles/900006444683
How to count the number of characters?
https://help.teachme.jp/hc/ja/articles/10268480807961
Can I edit a manual saved as a draft that exceeds the character limit for publishing on the web browser version, using the mobile app?
https://help.teachme.jp/hc/ja/articles/35795088098969