Key legal question
Whether the appeal could be entertained despite non-payment of the cost advance within the deadline.
Extracted holding
No. Because the appellant did not pay the advance or provide the required proof of timely payment, the appeal could not be considered.
Extracted reasoning
After the warning under Art. 62(3) BGG and the expiry of the non-extendable grace period, non-compliance required non-entry under Art. 108(1)(a) BGG.