I don’t pretend to understand the details, but pinging from different geographical locations will give different IP addresses.
The docs for the API say:
HTTP RESTful API
Blynk HTTP RESTful API allows to easily read and write values of Pins in Blynk apps and Hardware.
API description can be found here. Warning : Blynk HTTP API still has GEO DNS issue. This means, for now you need to use direct server IP instead of hostname in order to make it work with 3-d party services like IFTTT.
http://docs.blynk.cc/#http-restful-api
Pete.