No cup final appearance for Sevenoaks Town in the Southern Counties East League Challenge Cup this season.
The holders' first defence of the trophy ended in second round defeat after a disappointing display at The Bourne Stadium on Tuesday night.
They were a goal down at half-time, but Byron Walker's opportunist equaliser raised hopes of a recovery, only for Erith to score twice more, including a 90th minute penalty.
Sub Mark Jones came off the bench to net his first goal for the club - but it was too little too late.
Manager Micky Collins gave latest signing Jason Thompson his debut up front, while Billy Bennett started on the bench after picking up a knock late on in the win over Whitstable on Saturday. Jack Miles missed the game with a stomach bug.
Town started brightly with two teasing crosses by Harrison Carnegie, before strong claims for a penalty went unanswered with referee Nick Fruin awarding a free-kick on the edge of the box.
Erith served warning of what was to come when Steadman Callender fired just wide, then Andres Tobin saw his effort bounce off Craig Holloway's left hand post.
Tom Ripley's important challenge on Adem Ramadan stopped another break, Callender went close again before Osman Proni headed Erith in front five minutes before half-time.
Collins sent on Bennett and Tom Youngs in place of Paul Springett and Rory Hill.
The latter booked inside the opening half hour - looked in trouble after going in heavily on Erith keeper Adam Molloy.
Mr Fruin spoke to his assistant and then called Hill to him - with many people expecting punishment, but none came.
Walker made it 1-1 after 66 minutes making the most of a mix-up between Molloy and a defender.
However Town were behind again six minutes later when Gannon fired home after another effort had been cleared off the home line.
Bennett saw his shot saved - Erith sub Ryan Golding making it 3-1 from the spot.
Jones knocked in Town's second deep into stoppage-time.