If the software cannot be installed on the Symbian system, you can follow the following operations:

First, enter the mobile phone

Program Management ~ Options ~ Settings ~ Software Installation ~All, Online Certificate Check~Close.

In this way, you can install programs and themes in sisx and jar formats.

If there is a certificate expiration problem during the installation process, you can adjust the phone time forward in years until the installation is ready, and then adjust the time back after the installation is completed.

If the above settings are invalid, you must create a certificate.