SEPA Mandate not visible on Contact anymore
Welcome to Stack Exchnage Hans-Christian.
The latest version of CiviCRM contains changes regarding the display of custom tabs in the contact view that also affect CiviSEPA. You should be able to fix the described issue by upgrading to the latest CiviSEPA version (1.5): https://github.com/Project60/org.project60.sepa/releases