Thank you @leprechaun and @jaxsonmurph, you are both godsends! This was literally doing my head in and between you both, you have resolved this for me. POB tokens successfully staked :-) If anyone else is having this issue, please do read @leprechaun reply to this post and also read @jaxsonmurph new article on read.cash. They are both worth following for their knowledge and support.
Removing the Hive keychain wallet extension from chrome and then adding it back using my master password, as suggested by both of them (which is the one that looks like a private key but is not the private key), has allowed the Hive keychain to connect with all of my keys: private, active and posting and allowed me to stake/power up my POB and not lost any of my token balances! Can't thank you both enough. I can sleep easy tonight lol.
You are so welcome I am just glad to see you have resolved the issue and managed to stake your #POB I am chuffed for you this is a huge moment.
I am hopeful others will read your experience and learn from yours and our mistakes, my post can also be found on [https://www.proofofbrain.io/hive-150329/@jaxsonmurph/a-quick-post-for-newbies-having-problems-staking-and-powering-up-hive-an-pob