Old iPhone 11 will not erase

[C_Dickson]

I have upgraded my iPhone but can erase my old phone(iPhone 11) in order to prepare it to sell. I can reset 'all settings'.

When I attempt a reset I get the following error message: 

                                "An Unknown Error Occurred

                                      Please try again later"

I have also tried connecting to my Mac but the iPhone does not appear in my laptop to allow me to erase it.

Is there any way to force the phone to erase? 

[MI5 · Accepted solution]

@C_Dickson 

You need a data connection to do a full erase. Wifi will do if you have removed your sim, although having a sim in is preferred.

Also check you are entering your correct password.

[C_Dickson]

Many thanks. Reconnecting to wifi worked after adding my Apple Id to the old phone. 

[MI5]

You're welcome @C_Dickson