There are several possible causes:
You logged out without using "Save Draft", "Publish", or "Update"
Draft data that has not been "Saved as Draft", "Published", or "Updated" is only stored on your device and will be deleted when you log out.
Additionally, Teachme Biz sessions expire after a set period (*) and require you to log in again.
Before logging out, make sure to "Save Draft", "Publish", or "Update" your content.
*You can select from 12 hours, 3 days, 7 days, 30 days, or 90 days. The default setting is 7 days.
Related:
Create and edit manual (iOS version)
https://teachme.jp/8/manuals/3204679
Create and edit manual (Android version)
https://teachme.jp/8/manuals/3204850
What is Session Management?
https://help.teachme.jp/hc/en-us/articles/900006443883
You synchronized incorrectly when data was in conflict
Since the mobile app allows you to create and edit manuals offline, there may be conflicts between your device data and server data.
If you make a mistake during data synchronization after a conflict, you might accidentally overwrite your manual with unintended data.
If you see a message like the one above during synchronization, be sure to check whether you want to keep the "data on the device (local data)" or the "data on the server", and synchronize according to the reference below.
What does "Not Synchronized" mean in the Mobile App?
https://help.teachme.jp/hc/en-us/articles/12095601263769
You're checking the manual content on a different device than the one you edited it on
When checking edited content on a different device, even with the same account, you need to save the data to the server.
Make sure to "Save Draft" on the device where you made the edits, then synchronize on the other device to see if your edited content appears.
Related: Synchronize with the server (Mobile App)
https://teachme.jp/8/manuals/10717036
Multiple users edited the same manual simultaneously
When multiple users edit the same manual simultaneously, the content from the person who completed their editing last will be reflected.
As a result, your edited content may not be reflected.
Please check if someone else is editing the manual at the same time.
You're logged in with the same account on multiple devices
While you can use a single account on multiple devices (smartphones, tablets, PCs, etc.), simultaneous use is not recommended.
If you access from more than a certain number of devices, devices with the oldest access history will be forcibly logged out, and content being edited may be lost.
Reduce the number of devices you're accessing from when editing.
Related:
How many devices can I use at the same time with the same account?
https://help.teachme.jp/hc/en-us/articles/900006442043
What should I be aware of when sharing an account with multiple people?
https://help.teachme.jp/hc/en-us/articles/4411464955673