First of all, you do not need a PIN code to connect, you only need to use the Perifit app.
If you have been prompted for a PIN, click cancel and return to the application.
To be clear, do not go into the Bluetooth setting of your phone, the connection is completely handled by the Perifit app.

If you still have an issue, try to update your Perifit app, this might solve your connection issue (go to the App Store or Google Play Store and look for Perifit).

If updating the app did not solve your issue, use the email button inside the Perifit app and send us an email with it. This will allow us to see what is going wrong with the Bluetooth connection. We will get back to you within 24h.