As I said, dirty flash from A11 to A12 is not recommended and not supported. Most (All) people will have problems like the user above @Zeebeest1 and to avoid confusion people must follow the instructions the developer gave.
And generally from one Android version to another recommended is clean install.
Read the Magisk Installation Instructions on GitHub. (Scroll to the end which says "Custom Recovery")
You can rename the .apk to .zip or you can find it my POCO F1 Ultimate Collection & Guides thread. Sideload via adb with PE Recovery working fine.