Unable to deactivate old Apple ID on iPhone 5s for reactivation
I want to re-use my old iPhone 5S, but it is actiavated to my old apple id that I no longer have access to. I enter my information at https://al-support.apple.com/#/al/request and click on the link sent by mail, but the page shows "we found your device" but then it sais "Session Expired Please enter a valid serial number / IMEI / MEID." and I have no chance to enter any information.
How can I de/reactivate my iPhone and/or re-gain access to my old apple-id?
[Re-Titled by Moderator]
Original Title: Account-Unlock not working