updating the package_access field in csv file does not work

I’d like to protect my content with a membership level that requires a monthly subscription. When I try to do this via the spreadsheet, it does not work. On the listings that I have updated manually the cells currently have this value:

a:1:{i:0;s:1:”5″;}

when i try to copy this into another cell, it does not update the membership access package on the listing.

any thoughts?