Firstly, please make sure that you are holding your phone correctly and that you know where your NFC antenna is located. You will find instructions here: how can I find the NFC antenna on my phone?
If the problems persist, please contact our support via email. If you receive error messages from the app, please take a screenshot and attach it to the email.
In the femSense app you can also contact our technical support via the "Contact Support" function in the menu.