The theme cannot be saved – for example, after a Shopware update – so your changes will not be applied.
The cause is stated in the accompanying error message. Usually, you have configured a configuration field incorrectly.
Potential error messages:
All you need to do is correct the relevant configuration field. The error message may indicate which configuration field is affected.
You can alternatively validate your configuration:
Why hasn't this error been noticed before?
You may not have noticed this error in Shopware 6.6. However, with Shopware 6.7, the validation of the theme configuration has been significantly improved so that even minor typos are now reliably detected.
If you could not solve the problem, simply start the ThemeWare® Debugging. You can open a support ticket in case you are not able to solve the problem yourself: