The provisions of Section 5 of the Limitation Act, 1963 have not been expressly or impliedly excluded by Section 107 of the GST Act, 2017.
Therefore, in my humble opinion, the First Appellate Authority has the discretion to condone the delay in filing the appeal.
I reserve the right to be wrong. ~ Abhishek Raja Ram, 9810638155
Abhishek Raja "Ram"
@abhishekrajaram
MEC, STBA Delhi || Speaker and Author on GST. Life dedicated towards Tax and Economic Reforms & Simplification