If you are not able to make payment online on IRCTC ticket booking, here are some possible solutions:

1. Check your internet connection: Make sure that you have a stable internet connection before attempting to make the payment. A slow or unstable internet connection can cause issues while making the payment.
2. Check your bank account balance: Make sure that you have sufficient balance in your bank account to make the payment. If you do not have sufficient balance, you will not be able to make the payment.
3. Try a different payment method: If you are unable to make the payment using one payment method, try using a different payment method such as a different debit or credit card, net banking, or UPI.
4. Contact your bank: Sometimes, your bank may have placed a hold on your account or card due to security reasons. Contact your bank to check if this is the case and to resolve any issues.
5. Try a different browser: If you are still unable to make the payment, try using a different browser to access the IRCTC website.
6. Contact IRCTC customer care: If none of the above solutions work, you can contact IRCTC customer care for assistance. They can help you troubleshoot the issue and guide you on how to make the payment.

It is important to note that the IRCTC website may not be available at all times, and may be subject to certain terms and conditions. Make sure to read the terms and conditions before using the IRCTC website.