Versions of the SLP, WP, Power add-ons?
Can you show an example or snippet of the file you are importing?
Are you looking at back end and seeing a location does not have both address lines or are you saying the results on the front end?
(see attached, I just imported the csv file adding a second address, I then checked back end locations it was there, I just checked front end under results and it was also there, my test : Positive results, worked as expected)
I did not change my results layout so I should change the results layout to put address 2 on separate line but other then that it shows up correctly, imported correctly anon both back and front end
Do you have address 2 checked off under screen options?
If you include the site url that the results page returns I can look at it there as well.