I just managed to get it to work after fighting with it all morning.
I did the following (on my Android device, as Chrome currently does not have the proper icons in place to make it work): - be aware clicking is the same as touching.
1. Logged into PL, from the Charachter select screen, went to Spacetime Nexus.
2. went under "My Account" then clicked on "Facebook Options"
3. clicked on "Connect" - PL then passed focus on my phone to facebook, where it requested my permission to allow "Pocket Legends" access to my basic info and to allow to post as me. Obviously you have to allow.
4. control passed back to PL - logged in again, from Charachter select screen, went BACK to Spacetime Nexus.
5. went back under "My Account" and then "Facebook Options" - at this point i noted that it still listed me as "logged out" underneath the facebook connect icon - so i clicked on "Connect" again. This time it passed control to facebook, but then after going through a loading process, it passed control right back to PL and now the facebook options screen showed "Logged in" for facebook.
6. Now i went to the "Offers" tab and clicked on the 2 plat offer for liking PL on Facebook (i made sure to "unlike" PL beforehand) - clicked on "Like" once the PL facebook page had appeared on my screen
7. hit "back" which sent me back into PL, once it loaded back up to the char select screen, i received a message stating my 2 plat had been added to my account, which i verified after logging in!
Hope this step-by-step helps others out there take advantage of this deal and makes the processes somewhat less frustrating for you!