This is a follow-up report. I have solved the problem.
The problem seemed to be related to the fact that the destination notebook was not displayed, so I created a new notebook and created a new note there.
After that, I found out that it is possible to create a new note in an inherited notebook that is not a new notebook, as long as it is a notebook other than the main notebook.
Initially, the main notebook did not appear in the selection screen (it was blank) and could not be selected, but after organizing the notebooks and syncing them, the notebook list is now displayed correctly. Then, I selected the main notebook again and tried to create a new notebook, and it worked fine.
It may be that the number of notes in my main notebook is more than 20,000, which may have interfered with the notebook list information or its data transfer.
Thanks.