One problem that occurs with the operating system on iOS, iPadOS, including watchOS, is that if the memory space is less than 500MB, it can't be updated. Apple now adds that if it's iOS 15, iPadOS 15, including watchOS 8 pg
The notification will say You can now update your device using Software Update if less than 500 MB of storage is available. (78474912) Apple did not provide further details on the issue. Especially in the case of large updates However, it is very easy to prevent problems that arise. Manage enough space to remove unnecessary apps, it should be enough.