@Raheel I wrote:
I am trying to hire someone but an error accured that is An error accured while processing your request. Please try again.
Have you verified your pament method? Are you using a proper credit card (not a prepaid etc card) or a PayPal account that is backed by a proper credit card?
This usually happens when people try to use their Payoneer or similar cards.
Please, add an alternative payment method and try funding a milestone and sending an offer again. Unfortunately, Upwork wasn't able to charge the payment method you have on file at the moment.