Not accepting same card which was declined

[Lossprevention]

Once my client’s credit card was declined the payment. My client said to retry the card and system is not even accepting it. 
not letting me charge one time payment either. 

[SVLFever]

As odd as this sounds @Lossprevention , I would recommend power cycling the device.  I have on extremely rare occassions seen an issue where the Register won't accept a valid card, and then continue to decline it.  Rebooting the Register fixed the issue.

Hope this helps!