1. The application does not support handwritten signature: the application does not have this function, so it cannot use the reserved signature of the horizontal version of the mobile phone. To ensure that the application or document editor you are using supports the handwritten signature function, you need to check its description or contact the developer for further assistance.
2. The mobile phone signature function is not turned on: In the application, you need to turn on the mobile phone horizontal signature function in the settings, and you need to ensure that the relevant settings have been correctly configured.