Aadhaar OTP is sent by UIDAI and is required during registration process to complete KYC. The phone number linked with Aadhaar must be same phone number used for application. In case the same phone number is linked with Aadhaar & still OTP is not received, you can try again after a couple of hours. This could be due to intermittent issues at UIDAI. 

If OTP issue persists, request to write to us at customercare@tataneu.com