Bought a MacBook Pro 6months ago and only turned on to set up. Went out of the country to work. But didn’t take my Mac. Since it was new to me. And took my windows. Got back and decided to use my MacBook Pro. But battery was dead. And won’t charge

Charge it for an hour or longer to see if it will go.If no joy, do an SMC Reset:

How to reset the SMC of your Mac - Apple Support

.

Try an SMC reset.

Try leaving the laptop plugged into the charger for a day or two to see if the battery will begin to charge. If it won't power on after charging for two days and an SMC reset, then you will need to have the laptop serviced.

If you are going to leave a laptop unused for any length of time you should make sure it has about a 50% charge, then completely power off the laptop by using "Shutdown". You need to make sure not to trigger the laptop back on by either opening the display or pressing a key. Even powered off, the system will still drain the battery a bit so for extended periods you need to periodically recharge the battery to 50% again (making sure to once more power off the laptop).

www.apple.com/batteries/maximizing-performance/