Check first you are typing the correct phone number:
1. A 10 numbers mobile phone number
2. Without input +91 country code
3. Can't input a local phone number
＊Correct example: 9876543210

If you checked you are typing the correct phone number, but you still can't login:

1. OTP system may be too busy, try again 5 mins later or use your password
2. OTP mail may be blocked by your phone, check your junk mail box and setting  or use your password
3. OTP mail may be blocked by your telecom, contact your phone service provider  or use your password
4. Password may be wrong, make sure you are trying again.
5. Your network may be disabled or not stable, try to move to an open space with fine network signal and re-open network connection again.
6. This phone number maybe has registered already, try to use login again
7. When you are using a second-hand phone number, this phone number maybe has registered already, try to use a new phone number instead.
8. When you are using a second-hand phone, this phone may be installed already, try to delete and clean app data, then install again.