After searching high and low for resolutions, I finally managed to login back to my Splinterlands account which I thought I lost it!
This is what happened!
1- I am new to the game, so I am trying to access my Hive account. So I requested my account key in Splinterlands.com
2- They send me the link and I gain access to my various codes which includes Master Password. Now the tricky thing here is that there is a note there stated "you can change your password ...." and thus for security reason, I decided to change and the nightmare begins!
3- After changed the master password on my Hive account (tips: you can only use the generate password feature for your new password on Hive), I found myself stuck with sea of red screen of death on my mobile app (yes! quite the same as blue screen of death in Windows where you have tonnes of codes on screen) and you have no choice but to quit.
4- Tried login via web - error appeared whenever you battle, or claim your SPS or try to rent out a card - the error is:
"There was an error publishing this transaction to the Hive blockchain. Please try again in a few minutes. Error: RPCError: Missing required posting authority: Missing Post Authority (username)"
5- You can try as many times but for sure the error remained! So it was all but confusing when they ask you to try few minutes later. It will never work! And you be stuck forever till I found my solution!
6- Before I shared how you can get back to your account, let me revealed what I found out which there is no mentioned what so ever in any site include Splintersland. I noticed when you change your Master Password, your other keys also changed such as Posting and even Memo keys! And this is the problem where when you tried to login to splinterlands with your email and password, the associated posting keys no longer valid!
7- So the solution is simply: Login with your username and the new Posting key! and it works like a charm! You can never able to login using your email and password anymore - not to what I known of at the point I am writing this.
So I learnt the lesson for wanting more security by changing my master password in Hive but end up have to stuck with loggging into Splinterlands using super long Posting Keys...so for anyone who has not change your master password but want to consider change, I hope you learn from here...thank me later!
Cheers!