I have a viper 5900 car alarm with the 7701 vpx remote and the lock and unlock are reversed. How do I fix this

If it is the OE (original equipment) key fob, meaning if it is the alarm remote control that came with the original purchase of the car it should not need reprogramming. If it is an aftermarket alarm then it may need reprogramming, more information is required to answer the question.
This is a common issue and the most common problem is that the solder joints holding the battery in the proper location. If any of these are broken the remote will not function. It can be fixed with a little solder or if your uncomfortable with doing it yourself, take it to a computer repair store (they can fix it ONLY if you have a broken solder point).
Take the key fob to the closest auto parts store (aka. autozone, o'reilly's, advance) and near the counters they have a key fob testing equipment (FREE). If the remote is working a light will blink when you push the key fob button while close to the testing equipment. If the testing light shows that the fob is working but does NOT unlock your doors, it needs reprogrammed. If the testing light doesn't blink at all, repair or replacement of the key fob is indicated.
Hope this helps and good luck!

try disconnecting the battery for a minute.

http://www.directeddealers.com/manuals/og/viper/G5301V_05-06post.pdf
the 7701V is actually the remote. The Viper remote start alarm system that it corresponds with is the Viper 5900.

If you are not getting any sound then the system may be in valet. To find out if it is in valet your status l.e.d. light should be solid and not flashing. if the light is not even on then maybe your horn was never hooked up, but if the light is on then you must take it out of valet.To take it out of velet you have to turn on the ignition of the car and then shut it off... With-in 5 seconds you have to press the valet overide button. The status light should go off when you do this. The other way of taking it - in and out of valet is to open a door and press the.... lock..unlock..lock unlock... lock butons in that order.

The 7701v remote is listed for use for two systems and you can download the manuals via the following links.

Viper 5500 owners manual

Viper 5900 owners manual

Try reprogramming the remote. Open the door, turn ignition on, press and release valet switch one time, then press and hold valet switch while pressing lock button on remote.You should hear a confirmation chirp from the alarm. Release both buttons.Turn off ignition. test.

sounds like the alarm went into valet mode. that's usually what a solid blue light means on most viper alarms. check your owners manual on how to take the alarm out of valet mode. with the 5701 alarm its usually done with the remote. hope this helps

try a couple of things, 1) try unplugging the anntena for the alarm for about 5 minutes. 2) remove battery from remote for 5 minutes 3) reprogram the remote

Try to relearn the tach by cranking the car and holding the valet switch(small black push button) until the LED lights solid.The try it again