I'm so happy today! My Aadhaar is Finally unlocked. I didn't go to the Aadhaar Center. Instead, I found out through Twitter/Reddit that you need to contact UIDAI by sending a message (DM) to 1947. Tell them you're unable to get an OTP on your locked Aadhaar and share your Enrollment Number with them. If you don't share it, your issue won't be resolved. If you do share it, they will resolve it within 48 working hours by sending you your new Virtual ID. I also went to the Post Office 10 days before though to update my mobile number, so maybe that helped as well.