How do I pay for a police character certificate if the payment failed?
In some countries, payments fail rarely owing to server outage, network outage and other technical reasons. In these countries, if your payment fails, there’s a strong possibility that your credit / bank balance is not good enough even for the relatively measly fees charged for Police Character Certificate. That could lead to a negative perception of your character, which will make it very hard for you to get a PCC.
On the other hand, in some other countries, especially those where two factor authentication is mandatory for online payments, payments fail regularly due to technical reasons. More in Why Two Factor Authentication Is A “Conversion Killer” & “Blood Pressure Booster”. In those countries, you should simply keep retrying the payment until it succeeds. That will suggest that you’re tenacious / perseverant. Since those are generally perceived as good character traits, you should be able to get a PCC quite easily.