Please read this JDocs FAQ page to learn more about this issue and its fix.
IMPORTANT information for users who have already updated to 3.9.9 and faced this issue.
Due to a bad sql update, the template style mapping to content languages has been lost. Unfortunately, this is an unrecoverable error.
You must either:
We would like to take a moment to apologise to our users.
Whilst we understand that a release which introduces a major bug is always serious - in this case the bug involved actual data loss from sites, this is a red flag for us. We are going to pause and look at how we can improve our release and testing strategies and report back to our users when this is complete, detailing how we aim to improve in the future.
At this early point though we can confirm that this bug was introduced during the development of 3.9.9 and unfortunately was not picked up in the week between the 3.9.9 Release Candidate and the 3.9.9 stable release.