The message says that the content could not be updated. Unfortunately, it is not easy to determine why this happened. There could be many reasons for this.
Check under Tools > Site Health to see if there are any abnormalities there.
You could also try deactivating all plugins to rule them out as the cause.
Alternatively, check your hosting provider’s error log to see if any errors are listed there. Your hosting provider’s support team can help you find the error log.