If this is on a mobile phone, then try it on a pc. I've seen more cases where that made a difference. I don't know why though.

I tried from PC also but unfortunately this message showing again and again i don't understand what's the Issue, last year I book from same debit card and the experience was so smooth I can't explain but this time it's pathetic 

I am facing this error while buying EUrail pass for my tour how to solve this issue as I also tried from PC and different browser but the result are same

You could ask your bank whether they can see whether your payment was refused and if so for what reason.

Alternatively, try a reseller such as https://allaboard.eu/eurail

Okay Sure buddy thanks for great Support