I'm using BsmbI from NEB to digest a CRISPR lentiviral plasmid so I can insert my gRNA sequence. The digestion isn't working at all despite extending the reaction time to 1.5 hours. Other answers on Research Gate have suggested running the reaction at 37°C instead of 55°C to reduce degradation but I doubt this will help with my issue. Any help you can give me is greatly appreciated.

2ul NEB buffer 3.1

2ul NEB BsmbI enyzme

2ug of Plasmid

Total reaction volume 20ul