I installed the honeywll rth23oo today my old thermostat is also honeywell so i have only green,yello ,red and white wires which i connected to the right terminals but still it doesen't working

This may be of some help. https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-faq-northerheat-58313.html Are you getting power to the stat, if so how many volts?

Hi
Honeywell don't follow color code
Have u labelled the wires before disconnecting
If yes,then check for wires,pins and breaker
Should be tight and secure,furnace door should be closed
Also these stats works only if voltage is between 20-30 Vac
Get the voltage checked