Questione giuridica chiave
Whether the cantonal court correctly refused to hear the invalidity appeal for lack of a timely filed written power of attorney.
Decisione estratta
The non-entry decision was unlawful because a valid power of attorney had been executed within the deadline, albeit sent to the wrong authority.
Motivazione estratta
Submission to an incompetent authority still preserves the deadline if the filing is forwarded without delay; the claimant had substantially complied with the order to produce the power of attorney, and the missing receipt by the cantonal court could not be held against him.