Resolved Fix "Could not resolve host"

A client made an online payment for an Event Booking event. The payment was successful, but the registrant didn't appear in Event Booking. In the log file of RO Payments I found this part about the transaction:

[2024-11-19 12:31:36] User Guest is calling.
[2024-11-19 12:31:36] Going to sleep
[2024-11-19 12:31:37] Waking up
[2024-11-19 12:31:37] Going to sleep
[2024-11-19 12:31:38] Waking up
[2024-11-19 12:31:38] Going to sleep
[2024-11-19 12:31:39] Caught an error notifying extension: Could not resolve host: xxxxxxx.xx
[2024-11-19 12:31:39] Trigger callback on extension addon: Event Booking
[2024-11-19 12:31:39] Setting payment as processed
[2024-11-19 12:31:39] Waking up
[2024-11-19 12:31:39] Result: SUCCESS

What does "going to sleep" and "wake up" mean? Is this from Mollie or RO Payments?

And what can I do to improve this error "Could not resolve host: xxxxxxx.xx"?