Need your help urgently, can't log into MS ( Never had this issue).

Could you please give me more details, and explain how to do that?

Simple. Playing MapleStory from Steam is the same thing as clicking the launch button from the website. Though, this has its perks.

Step 1: Go to http://store.steampowered.com/
Step 2: Create an account with Steam and download it
Step 3: Search MapleStory (Here's the link in case you need it: http://store.steampowered.com/app/216150/)
Step 4: Press PLAY GAME to download the game onto your Steam account (Note: you will be redownloading Maple essentially)
Step 5: Launch MapleStory from your Steam account. It will be located in your LIBRARY Tab at the top.

I didn't run into any issues when I first played from it, and Nexon just recently fixed the Steam Launcher. Been playing just fine with it again.