Whether the appeal could proceed despite non-payment of the advance on costs
No. Because the appellant was warned of the consequences, did not request an extension or legal aid in time, and did not respond when invited to explain the missing payment, the appeal had to be declared inadmissible.
Under the applicable cantonal and federal rules, an advance on costs is generally required in social insurance appeals. If the advance is not paid within the deadline, and no timely extension or restitution grounds are shown, the court may not enter into the appeal.