@mmaydan wrote:
It was updated recently. Does not turns on. Just is playing rotten apple logo on-off with no further action.
The phone could be blacklisted (registered as lost/stolen/etc) and deactivated. If so, it will do nothing other than Emergency calls and (if the owner enabled the feature) sneakily run "Find My iPhone" in the background.
If you bought the phone new in box then it's likely not blacklisted. If you bought it used or obtained it from another owner then you just can't know unless you look up the phone's status at an online database. You'll need your phone's unique IMEI.
https://imei.org/check-imei/blacklist
https://support.apple.com/en-us/HT204073
The phone could have been bricked or soft-locked with a bad, broken, or incompatible update. It happens sometimes. It's easy for end-users to follow the prompts but still get stuck installing a malfunctioning update for the wrong version, wrong device, or wrong region.
You can try restarting it while holding the "secret" button combination which invokes built-in diagnostics and recovery mode. This will do a firmware rollback if needed. It will likely also do an unavoidable hard-reset, aka "factory reset", which erases all user data from the device. If the phone is still bricked after this then your only options are to throw it away, take it to a repair shop, or interact with Apple's "genius" people.
https://support.apple.com/en-us/HT210616
