It appears that your console is parental locked. You can call Nintendo but that takes time so I’d suggest you use this procedure instead:
- Go to settings and see if you can get the parental controls prompt to pop up
- Choose forgot password on the bottom of the keyboard
- In the security question, choose forgot again
- Make a note of the Inquiry number
- Go to https://mkey.salthax.org/
- Choose 3DS
- Put the current system date (in case it’s wrong or something
- Leave Additional Data empty
- Put the number you made a note of above in the Inquiry Number field and hit Go
- Take the new number and put it on the number field on your 3DS
- The console should now be unlocked, go to the parental controls menu and disable it fully.
I hope this helps! If you have any questions feel free to report back (pictures of your screen are preferred so the community can understand better.