Assuming that you are a windows user:
1. Connect your Kobo
2. Navigate to KOBOeReader/.kobo, there should be a file name KoboReader.sqlite (copy the link)
3. Download
https://sqlite.org/2019/sqlite-tools...86-3280000.zip, and unpack it.
4. Open command prompt in the folder above.
5. sqlite3 (paste the link)
6. copy and paste this: INSERT INTO user(UserID,UserKey) VALUES('1','');
7. type .quit