Same here. Found this thread and would propose to continue there: Invalid private key for encryption app. Please update your private key password in your personal settings to recover access to your encrypted files
BTW, the German translation does not match the English error message. What shall be updated? The private key - what would be the translation of “privater Schlüssel” - or the private key password, as it is called in English? In Security/Sicherheit settings only passwords can be set.