These Section 3 violations are always vague and oft-times difficult to figure out.

How old is your account? Have you been actively selling prior to your deactivation?

Is there anything that needs to be verified in your account? Do you have a valid credit card on file? Have you received disbursements? Has any of your information changed that either needs updating or that you recently updated?

This text from the notification makes me lean in the direction that something might be missing.

"Why did this happen?

Your account does not meet the requirements of the Amazon Services Europe Business Solutions contract:"

I'm not at all familiar with the requirements that might be specific to a German or European account but think along those lines to see if you can come up with anything.

Do you have any unaddressed policy violations? Check your Performance Notifications, emails and Account Health Dashboard, including all the links along the top, for anything you may have overlooked.

Have you had any interaction with Seller Support, a buyer, a fellow seller that might be construed as inappropriate?

Anything you can think of as far as documentation Amazon asked for which you didn't provide? Any instructions that you didn't explicitly follow to a T?

The list goes on and on. Do a search for Section 3 on the forum to see if anything else from another thread might pop out to you.

The other thing that stands out is Amazon only gave you a path forward if you believe the message was sent in error and not a path forward or any instructions to correct anything. That in itself is concerning.