If they mean you have an open gap, then you’re only recycling the air around the furnace. It needs to be sealed up. Mainly, it will allow all the air in the whole house to circulate properly. If you can find a reputable company and it’s just a straightforward fix, it shouldn’t cost very much more than a basic service fee. I recommend scheduling it right away, only because the trades are all still very booked out. It should be fixed prior to turning it on this fall. Are you on nextdoor? Your neighbors will have the best local recommendations - and warnings of dishonest companies. Good luck.

Thank you for the info! our inspector said that it ahould be an easy fix but i have never dealt with this before so wanted to confirm.

Most likely it is something you can fix yourself. Small gaps in duct connections can be fixed by applying tape to seal the joints. If this is the only thing the inspector flagged when inspecting the furnace then consider it a good thing.