I'm running the latest version of Logos for iOS (2.0.2), on an iPad with 5.0.1. I have UBS4 opened (downloaded) to 1 John 2:26 (the top verse showing on the screen, navigated to by the "Contents" popup).
I touch and hold on ὃ, the 5th word in v. 27. It highlights and the popup appears. I press "Lookup". The window says "Looking up ὃ ...". When it comes back, I've got the parsing information for the next word ( ἐλάβετε ).
I'm really loving having the UBS4 and being able to use "Lookup" to verify my parsing, but I need it to work correctly. 
Thanks,
Donnie