Following worked for me
Connect iPhone/Device to mac.
Open XCode > Window > Devices and Simulators.
Under devices select the "+" icon in the bottom left.
Select your device and click Next/Done.
On the iPhone make sure you don't have settings open (i.e. force close it.).
Open settings > Privacy and Security
Scroll to the bottom and Developer mode should now be there.
My problem was with step 5, I already had settings open and for what ever reason developer mode wasn't showing so had to exit and reopen settings.
StringyGG
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