At the time of goods released I was having a valid NAFTA certificate. It was a CLVS shipment. At the time when B3 submitted to CBSA the NAFTA was expired. Please advise.

Please be advised that NAFTA should be active at the date of release. CLVS shipment are submitting to CBSA later (by the 24th day of the month following the month of release). So in your case everything is good.