The mobile phone will have a certificate when it leaves the factory. If the certificate expires, it means that the mobile phone version is too low to support downloading this software, or the service period of software signature has expired.

You can upgrade your mobile phone system or switch to a lower version of the software. If the software can't be installed, move the date in the mobile phone forward for a few months, and then adjust the date back after installation. If the prompt expires, you can adjust it forward again until you can download the software normally.