Custom extensions are not allowed. The license is invalid, is expired or doesn't permit it. Url: %1
Custom extensions are extensions that you create, such as to customize the layout of an invoice, that do not link to the banana.ch site but are saved in a local folder.
To use this type of extension you must have the version of Banana Accounting + Advanced plan, or use the application in Demonstration mode, for example limiting accounting entries to 70 lines.