If your notes are automatically deleted, there is a good chance that the use of a browser extension is the main cause.
Indeed, some extensions can cause the following problems:
Unable to write notes because the text is erased
Deletion of note content after saving
Unable to save language settings
To avoid these problems, we invite you to check that your browser does not use one of the following extensions:
Google Translate
If you are using Google Translate, please disable this browser extension.