QR Code and NFC tag link to custom GPT not working

Hi there! I’m desperate to figure this out - I created a custom GPT and then a QR code that links to it for school, it is supposed me directly to it and other times it takes me to the general ChatGPT-4 screen. I double and triple checked that its the correct URL when generating the QR codes, but it’s still not working. Is there any reason why this would happen and how I can fix it or work around?