To release a Manual, the following conditions must be met.
At least one Step is registered
At least one Step is required, separate from the cover page.
If there are no Steps, the message "Please create at least 1 step." will be displayed.
A Title and image (or video) are registered for the cover page and all Steps
If any are not registered, the message "Some areas have not been completed." will be displayed.
The Title and description are within the character limit
If the limit is exceeded, the message "Please keep the text to ◯◯ characters or fewer." will be displayed.
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Related: An error "Some areas have not been completed" occurs during Release even though the Release conditions are met
https://help.teachme.jp/hc/en-us/articles/900005509566
Related: What is the maximum number of characters that can be entered in a Title or description?
https://help.teachme.jp/hc/en-us/articles/900006444683