As of December, OP-mobile and OP Business mobile require at least Android 10 or iOS 17 operating system. The reason is that equipment manufacturers no longer update the data security features of older operating systems.
With some devices, you can update the operating system yourself, using the device settings. The settings also indicate which operating system you are running. However, with some older devices, updates are no longer possible. If you have such a device, you must install OP-mobile or OP Business mobile on a device that runs on Android 10 or iOS 17, or a newer operating system.
Newer devices usually function better than older ones, and equipment manufacturers also update the data security features.