I had this problem with my Wildwood X-Lite. I took a look and found that the screen door handle frame has getting hung up on the door strike, causing the screen door to stay shut when you opened the exterior door. In my case, both the handle frame and strike were adjustable. I moved the two away from each other little by little until the strike didn't interfere with the handle frame. Now the screen stays attached to the main door as it should. Hope yours is as easily fixed.
2015 Wildwood X-Lite 281QBXL
2009 GMC Sierra 1500 Z71 w/HD cooling