The easiest fix for not being able to turn off Stolen Device Protection on your iPhone is to address the underlying reasons that trigger its security measures, the most common being the one-hour security delay. To initiate the turn-off process, go to Settings $\rightarrow$ Face ID & Passcode (or Touch ID & Passcode), enter your passcode, and tap on Stolen Device Protection $\rightarrow$ Turn Off Stolen Device Protection. If you are away from a familiar location (like home or work), or if you have the setting configured to Always require a delay, the screen will show a Security Delay timer for one hour; you must wait this full hour, and then you will be prompted to authenticate with Face ID or Touch ID one final time to successfully switch the feature off. If the option is greyed out, first try turning off any VPN you may be using or check Settings $\rightarrow$ Screen Time $\rightarrow$ Content & Privacy Restrictions to ensure it is not enabled, as this can restrict access to Passcode settings.