after upgrade to android 13, there is an exclamation mark on cellular icon. it dissappears when i enable mobile data. how to fix this?
There is nothing to fix. The exclamation mark is just the way Android 12/13 tells you that your data are disabled. I think in Android 12 it can be disabled using Gravity box, or via the options on custom ROMs, but gravity box has not yet ported to work in A13 (at least the last time I checked))