- IMPORTANT STEP! Create a backup of your website.
- Switch to the default theme such as "TwentyTwenty" by going to "WordPress Dashboard > Appearance > themes".
- Go to "WordPress Dashboard > Plugins" and deactivate all plugins except Toolset and Toolset add-ons.
- Check if you can still recreate the issue.
- If not, re-activate your plugins one by one and check the issue each time to find out the plugin that causes the problem.
- Please go to Toolset > Post Types.
- Click the title of the custom post type in question.
- Scroll down to the "Sections to display when editing".
- Check the "Author" checkbox. (check the attached screenshot)
- On the right side, click the "Save Post Type" button.
- Go back to the edit screen of the post type in the question and this time you will see the Author option to change.