If the payment has failed/ not successful due to technical error, then the application fee will not be paid to the TNEA authorities and your application will remain in pending status and you will get the refund of the amount (if it was deducted from your account) according to the bank's terms and conditions. Now, you can pay the fee (if you want to get registered for TNEA) by logging into the TNEA  portal and clicking on pay fee option.

Hope it helps.