New battery-Turn the key-Nothing

[notdavidspade]

I'm not sure that 6 volt batteries are sold charged.  And since the battery tender is just a trickle charger, it could take several days to build a charge.  As said below, put a volt meter on the battery and see what you have before going though your wiring. 
Good luck!

[David Pollock]

You will likely find the trouble between the starter terminal and the ammeter. The body of the car takes its power unfused from the starter terminal. This wire goes through the firewall and up under the dash. It is very vulnerable to abrasion from the parking brake mechanism as are the wires that are bound to it in a "harness".
From the ammeter, power is sent to the ignition (unfused) and to the headlight switch (fused) 

To trouble shoot, run a jumper from the starter terminal directly to the ammeter.  It is also possible that the ammeter has an open circuit, in which case bridging the terminals would restore power.  Two modifications are recommended once you have everything up and running. The first is a fusible link or better, a self closing circuit breaker (30 amp such as power windows use) right near the starter, before the main lead disappears into its harness  and the second is a discreetly placed ground strap bonding the engine to the body.  dp

[36 Ply]

Check the battery with a voltmeter to be sure that it is charged up. It may have sat on a shelf for months before you bought it.

My son bought a new battery at Wal-Mart recently; after 3 weeks, it would go dead overnight; then it failed a battery load test.

I would recommend checking it with a voltmeter; if it is charged up, then do a load test on it.

Also, does your car have a "main" fuse that may be blown?

Regards, and good luck,

Pat O'Connor

[Pandanom]

Check for a good ground from the battery. Follow the ground wire on the battery to where it is grounded on the frame, take it loose and clean it good. If that does not fix it get a wiring diagram and follow the current path from the battery.

Good Luck

[DENNIS P NOLAN]

Once again. I am inlisting your help. I have a new battery in my '39 P-8...with the battery tender on it...and nothing-!!...no gauges...no lights...cables are clean..tight...Help-..Thanks,Dennis