TECHNICAL ERROR: unable to confirm the order PS V: 1.6.1.15

[jemspeter007]

Hello Dev, 

I am facing issue when i was making free product to sell. ( using virtual product selection). 

TECHNICAL ERROR: unable to confirm the order

Details:
Error Thrown: [objects object]
Text Status: error

I am using PrestaShop Version : 1.6.1.15 

PS: I am not using paypal plugin in my website.
PHP 5.6