According to our documentation the feature can only be enabled on request.
Please note: Since no standard Visio format exists due to an indeterminate amount of different Visio templates, a problem-free import to Signavio can not be guaranteed. Each item in a Visio document has an individual ID. The Signavio Visio Import uses a BPMN template and corresponding ID mapping. If the Visio models deviate from this standard, problems may occur when importing to Signavio.
If the import should not work as expected please contact our Consulting team via firstname.lastname@example.org.
Find the German version via the following link: Import von Visio-Dateien.