There are a lot of explanations:
- Your spam filter may prevent the email from arriving (you should be able to find it).
- Your mail provider's spam filter may reject the email (you won't be able to find that).
- You have registered with another email address or changed the email address at some point of time.
- You may not have registered an account on www.soscisurvey.de, but on a local university server.
I guess that you have registered a new account to ask this question? I see a second account with the same name, using an university email address.
The server logs tell me that today 13:42:08 (UTC) an email was sent to the university server, and accepted for delivery. If it did not arrive, the error is on the universities side. I will send you the message details via email.