“OK” in success postback

Hi,

“The Verotel system expects “OK” response within 30 seconds. If no such response is received, an automatic refund is initiated” (https://controlcenter.verotel.com/flexpay-doc/purchase.html#success-postback)
Verotel customer services says your plugin adds a line before the “OK” response and all of my customers payments are refused by the system.

Any ideas or solution to fix this, please?

Thanks,

Regards