visual studio 2012 - Update target button is disabled after schema comparison -

i have created database project using vs 2012. once schema comparison done, update target button should enabled sync target.

but it's not getting enabled. plz.

i'm using vs 2012 sp 3, sql server 2012,

check in error list if have error, have non recognized word in vs (but in sql server), commented out, re-compared , enabled successfully.