Just bought a 2000 beetle

welcometomyturbodies

You could try leaving the key in the ignition in the on position for 30mins or disconnect the battery cables and tie them together for 30mins and if they don't work you could try the troubleshooting faq

http://www.myturbodiesel.com/1000q/multi/immobilizer-VW-Audi-FAQ.htm

Sounds more like a flat battery or maybe needs the terminals cleaned, the immo allows the car to start then it cuts out after a second or two.

That's excellent, I only know of it because someone else was on here recently with similar issues and they tried this after reading about it and it worked for them. Nobody seems to be very clear on what it actually does but only that it can work.