I had a problem this week, meter 'out of order' sign next to it mentioned Ringo.
I phoned the number on the payment sign next to the meter, was told immediately that my phone number would not be accepted because of a fail to pay previously. There is a chance I used the same system when I parked in another city 2 years ago BUT I know that payment went through. Certainly debited my credit card that time. Can't remember if it was Ringo, but I am guessing likely it was.
I then went to the Ringo website but could not get the Ringo website to accept my account, it said I had an account, then it told me I failed registration, then it told me it could not do a password reset, then told me I had registered.
I needed to be somewhere at a specific time, so I moved to the next car park which had a fully functional ticket machine.
Parking without a ticket risks a fine.