Try these steps in sequence to resolve the sign-in issues:
Verify that you are using the correct email and password combination. If you have more than one Amazon account with the same email address but different passwords, use the corresponding password for each account.
Ensure that there are no extra spaces in your password. This can happen when you copy and paste your password from somewhere else.
Verify that you entered the most recent Two-Step Verification code you have received, if you are prompted to enter one. Older codes won't work. For more information, see Two-Step Verification.
To reset your Two-Step Verification follow the steps here
Clear your browser cookies and cache or try logging in with a different browser or device.
Use our Password Assistance page to verify whether the email address you are using is the one registered in our system.
If yes, change your password using the Password Assistance page.
Log on to Seller Central using your new e-mail/password combination.
If these steps do not resolve the sign-in issue, it is likely that your email and password combination is not associated with an active Seller Central account. If you did not deactivate your account, click on the button below for assistance:
Additonal sign-in troubleshooting
I forgot my password.
Use our Password Assistance page to change your password.
Please do not create a new Seller Central account.
Note: If you change your password and are using something other than Seller Central (for example, Amazon Merchant Transport Utility) to submit product-related and order-related data, you might need to reconfigure those services with your new password.
How do I access my company's Seller Central account?
If your company has already registered with Seller Central, your company's account administrator can set up a user account for you.
If your company has not signed up to use Seller Central, visit www.services.amazon.in to find out how you can get started.
How do I get technical support for my account?
If you already have a Seller Central account, contact us using Seller Central. You must sign in first.
What happens if I don't receive my Two-Step Verification code via SMS text message on my cell phone?
Click the “Didn’t receive the code?" link on the webpage where it asks you to enter your code. This will list any back-up methods you designated when you set up your account. If you do not receive the SMS text, you can opt for a voice call to your registered cell phone number. If you do not receive a code during registration, check that the provided phone number has no typos and includes a region code and that your cell phone is able to receive SMS text messages.