Y E S 

BTW, our hearing is just fine around here...

If I hear you correctly, yes but only three years are open so you would be able to e-file 2017 for another month or so until the IRS shuts it down next month.

Just to add to what Anna says, you can and it's limited to the prior 2 years as allowed by the IRS' MeF.  And yes, it will cost you unless it was a return that you created before 2020.