failedTransaction error is "couldn't communicate with a helper application". What I can suggest to a customer?

I've got a customer who says he is getting "couldn't communicate with a helper application" error while trying to restore or purchase in my app.

This is not something that my app would produce and comes from func failedTransaction(_ transaction: SKPaymentTransaction) delegate method.

I do traverse the error in this method to show the most underlying one, probably not the best, but this is how I get to that "couldn't communicate with a helper application".

Interestingly, the customer reports that the same error happens on all devices with the same customer Apple ID, except the original iPhone where the original purchase was made.

I'll do better for the future versions with the error presenting and logging, but does anyone know what "couldn't communicate with a helper application" means in the context of failedTransaction(_ transaction: SKPaymentTransaction) delegate? What I can suggest to the customer?

This is the first time/customer that I'd encounter this issue with for long years passed.

Thank you for the ideas!