It would be more common to say, "can you please confirm my reservation". They should send you a confirmation number after your payment.

It has just come to my attention that there were insufficient funds on my card. I have now recharged it. Please, could you let me know if my reservation still stands? Thank you and I apologise for any inconvenience caused.

Tu frases no hay problema, por email a la hotel, esta vale. So quieres, tu puedes añadir: I have recharged it, can you try to take the deposit again please. Si tu realmente quieres sonido más formal, tú puedes deces, Can you confirm that I still have my reservation. Instead of : is my reservation still on. But your paragraph really is fine.

This is how I would write your email: I am so sorry. I had not noticed my card didn't have enough money. I have recharged It. If you could please let me know if my reservation is still on, I will really appreciate it. Hope this helps. :)