Just make sure you have a stable internet connection.
Follow the following troubleshooting steps:
From the PIN screen click on the "Need Help" button which is there at the right top corner.
Click on the "Logout" button from the message box.
If the issue continues, uninstall and re-install the app, and try to log in. If the error persists, please raise a ticket and our team will get back to you soon.
Disclaimer: Do not share your PIN or OTP with anyone. CoinSwitch will never ask you for your PIN or OTP.