Simple test plugin fails on checkout

[quantum-llama]

Hello VirtueMart People!

I stumbled upon an error, which slowly drives me crazy.

So:

Environment 1:

Package installed from VirtueMart, Joomla 3.6.2 with VirtueMart 3

Environment 2:

Joomla 3.6.5 from official source, plus VirtueMart from VirtueMart website (Core, AIO)

Environment 3:

Environment 2 + One Page Checkout from https://vmonepage.com/

I have a simple plugin which does, intended to do the following, echoing the following text "I'm alive!".

Here comes the riddle.

In Environment 1 and Environment 3 everything is perfect, but in Environment 2 it fails to var_dump the required text on the checkout page where users fill their details.

My question is why isn't my php file loads on that specific page?

It's not a php error, there's nothing in the logs, it simply just doesn't load.


I'm grateful for every crumble of information, because this is just maddness!


Cheers,
Greg