Try undoing all the changes you made.
I tried already… there is a revisions section, and I loaded the script from 2 weeks ago, still doesn’t change the footer.
This may be a plugin or theme conflict. Please attempt to disable all plugins, and switch to the default Twenty Twenty theme. If the problem goes away, enable them one by one to identify the source of the problem.
If you can install plugins, install Health Check. On the troubleshooting tab, you can click the button to disable all plugins and change the theme for you, while you’re still logged in, without affecting normal visitors to your site.
Deactivating contact forms 7 fixed the issue immediately!
Try updating that plugin.
If the issue still persists, then report the problem to the plugin’s author at https://wordpress.org/support/plugin/contact-form-7/