If you receive an error message during the checkout process stating that a signature could not be created, you will find the reasons here and how to handle them.
First, an isolated failure to create a signature is not problematic. The signature is automatically repeated by the system in the background. If processing slows down, a receipt can be created early so that the daily workflow is not disrupted. A signature creation will then either be performed automatically later or can be accelerated by you by recalling the invoice at a later time: If no error message is visible, the signature has been recreated and correctly archived.
This article is particularly relevant for users from Germany.