"To investigate the issue" means to carefully look into and gather information about a problem or concern in order to understand it better or find a solution. Full definition
Her work investigates issues of loss, appropriation, identity, and displacement, employing a range of media from collage and installed drawings to digital video. (saic.edu)
We are investigating an issue in which some users are experiencing the console shutdown after you turn it on. (neowin.net)
Many papers captured in our literature search simply investigated an issue related to climate change without taking a position on its cause. (theguardian.com)