I finally received into my Iberia account the balance of the voucher redemptions on Friday last week, although the transaction was backdated to December.

If you have multiple vouchers ensure you redeem each voucher individually, as the multi voucher redemption tool doesn't IME work.

The Groupon site is unreliable in saying whether a voucher has been redeemed or not. Some of my vouchers never showed redeemed, but the miles arrived eventually.

I contacted Groupon in no doubt dreadful Spanish using Google translate in January - got 4 cut paste holding responses over the next 6 weeks including one after I'd received the miles.

Paypal seem to have slightly different terms depending on the jurisdiction of your account, so best to check within your own paypal account website for disputing a non performing seller. FWIW, I have made a couple of UK PayPal disputes and provided you give everything they want, not had any problem in getting a refund.