Mostly it is because the file is too big. The current limit in the online form is 5 MB.
No problem: Send us all documents to vertrag@recht24-7.de. You can place your order in parallel (without uploading). We will then assign your order to the documents.
Or we will send you an upload link, with which you can easily upload documents without size limitation. Just send a short email to vertrag@recht24-7.de and you will receive the upload link.