[TYPO3-core] Troubles with extension updates in EM

[Christian Oettinger]

I seem to have found the reason in my case. LocalConfiguration could not be written by TYPO3/Apache. 
As easy as this is, I do not really understand, because I of course have installed and uninstalled Extensions before (which needs write access). Anyway, it definetely is the reason for me: setting write permission and/or ownership for typo3conf/LocalConfiguration.php solves the issue.

greetings and have a good day!
oe (Christian)