Yes, it should have asked you about multiple flight modes upon the first flip into SPORT. You'll also know when you're in SPORT when the VPS symbol turns red after flipping the switch.
Please ensure you enable multiple flight modes.
If still the same, please sync your flight records from DJI GO app and provide me with your DJI account email. I'll help to review it.
1- Ensure you enable multiple flight modes
2- Make sure the RC is back to P mode before booting it
3- boot the RC and select S mode in the RC
4- Enjoy the max speed in S mode