Invalid changeset UUID Wordpress

1. What does non-existent changeset UUID mean?
2. How do I fix non-existent changes UUID?

What does non-existent changeset UUID mean?

The Non-existent changeset UUID error usually is related to a mismatch or discrepancy of the WordPress Address (URL) and Site Address (URL). ... In that case you won't be able to login anymore and you would need to correct the URLs in your database or wp-config. php file.

How do I fix non-existent changes UUID?

Non-existent changeset UUID / Theme Not Accessible anymore!
...
To fix this problem :

1. Connect to your WordPress admin.
2. Navigate to Settings > General in the left panel.
3. Make sure your WordPress Address and your Site Address are exactly the same.
4. Save your changes.