Funds returned for \checking\" - no communication"

I am appalled with the service we have just received from Groupon. We purchased vouchers for 3 chalets in the Drakensberg. Vouchers were of R11 550.00, we received them accordingly and secured booking at the venue. Upon finishing all of that, Groupon returns the money. No phone call, no email explaining why that is done. When we reach them, we are told my sister in law whom we asked to purchase on our behalf was buying for the first time and it was a large amount. Groupon blocked her account because they had to check. Question - Who is this amount large for? Who determines the large amount? Is it because she is a black buyer? Oh Her account is apparently blocked for 48 hours and she has not been told why, except that they are checking!!!! What is being checked??? This is infuriating!!