Income Tax portal - Error faced while adding Demat account in profile section

The error is generally caused by a mismatch between the contact details (mobile/email) on your Demat account and those on your Income Tax profile; ensure these are identical, then use the "Re-validate" option in the "Failed Demat Accounts" tab after correcting any discrepancies.

The problem does not seem to be with the Demat Account but the technical glitch in the Income Tax Portal. First, check the PAN associated with your Demat account with the PAN on the e-filing portal. Other than that, make sure that you are entering the right DP ID and Client ID (NSDL) or Demat Account Number (CDSL) To validate the same, the Demat account should be active and linked with the same PAN as mentioned by the Income Tax Department. 

Try the following:

>  Clear browser cache/cookies and try in an Incognito window.
>  Clear cookies and try using a new browser (Chrome/Edge).
>  After a couple of hours, log out and log in once again.
>  Verify that your mobile number and email is current with your Depository Participant (DP).

If the issue is still not resolved, raise a grievance on the Income Tax Portal, inform your broker/DP (NSDL/CDSL participant) to ensure that your PAN, DP ID and Demat information are mapped correctly in their records. The mismatches on PAN and account details, and validation error at the portal are often the cause of similar cases. 

It could also be a problem with the portal temporarily as several individuals have recently reported problems with their profile being validated.