Above is a screenshot of the full error message.
I had this error in the TYPO3 backend after upgrading a TYPO3 website using the flux extension from version 10.4 to version 11.5. This error occured eventhough the templates from my provider extension had been correctly setup.
From researching, this error occured because the "Plug and play templates" feature of the flux extension was activated.
Solution
The solution is to deactivate the Plug and play templates feature. Follow the steps below to deactivate this feature.
- Login into the TYPO3 backend.
- Click on the "Settings" submodule found under the "Admin Tools" main module.
- Click on the "Configure extensions" button.
- In the modal that opens, click on the flux accordion to expand it.
- Search for the "Plug-and-play templates" feature and deactivate it.
- Scroll down until you see the 'Save "flux" configuration' button and click on this button to save the changes.
- After configuration has been saved, close the "Extension Configuration" modal.
- Reload the backend, and the error should be gone.
If any issues regarding this article, just get in touch with me via the contact form or via Slack(name: mbigha)