Payment showing in gateway as incomplete

My install is OC 2.3.0.2 with Journal theme (most recent version)

So, I have an installed the "free" Helcim payment extension. I applied the correct merch-ID and gateway token. Selected Order Satus field as "Pending" in the OC helcim payment extension.
As a LIVE TEST I entered an order (guest checkout), and on submit, when I look at the transactions on my merchant gateway - the transaction is listed as "Incomplete".
The OC error logs reference the helcim.php line 150 (paraphrased), as follows:

PHP Warning: print_r() expects at least 1 parameter, 0 given..../controller/extension/payment/helcim.php on line 150

Is this a situation with the payment extension, or on the gateway provider side?

Not sure where to go from here. Can someone provide any working suggestions on what I can do to troubleshoot and fix it?

Thanks,
GT