what does the passcode cannot be set (-1) mean?

Hello there lilinuk80,

Thank you for using Apple Support Communities! We understand that you are having an issue setting up a passcode, as you're getting error “ the passcode cannot be set (-1) “.

Do you know if you had any profiles installed on the device?

If this is not the case you may need to back up, erase and restore your iPhone to resolve this:

How to back up your iPhone, iPad, and iPod touch

Then restore it to factory settings:

Restore your iPhone, iPad, or iPod to factory settings

Then restore your backup and check your storage once the restore is complete:

Restore your iPhone, iPad, or iPod touch from a backup

We hope this helps! Have a great day!