Buy and pay later

Hi, I hope you can please help me.

I had a buyer email me to buy now and pay Friday. I said yes but the buyer emailed me back and said they had to pay straight away and my settings have to be changed.

I have checked my settings and can't find anything to change this.

I don't own a shop so could this be the reason why.

Any help would be greatly appreciated.

Thank you

Melissa