Just make sure you have a stable internet connection.
OR
Follow the following troubleshooting steps:
STEP 1:
From the PIN screen click on the "Need Help" button which is there at the right top corner.
STEP 2:
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.