Urgent ! android development, real machine debugging. Some projects can be some not

As the title : the first use of a real machine debugging android project , the first installation works very smoothly to the phone the above.
But when you want to install a second project, found not choose this device the phone . I do not know what causes it . Please prawns to the point .
picture is the second project , can not choose a mobile phone


ps: The first time you use the phone for debugging. Do not repeat the installation of applications.
------ Solution ---------------------------------------- ----
unplug and then plug try.
------ Solution ---------------------------------------- ----
phone that debug mode off and then open

check adb.exe start of the process is not, not in the words of the manual

then not restart the computer it is certainly not the problem
------ For reference only ----------------------- ----------------
hello
This project is able to succeed. Try again pull is still the same . There are other ways to do
------ For reference only -------------------------------- -------
pull cord is my trick up
------ For reference only ---------------------------------------
adb not disable it? Afraid of the phone burned ah ...
------ For reference only ------------------------------ ---------
find a reason !
1. connect the phone no problem. The device can eclipse the normal reality of my real machine .
2. restart the computer and mobile phone is still the same , you can not install the project is still the same can not be installed
later found to need a real machine can be installed and not installed the api works are not the same . Image.width



I sdk install this machine is the latest api19 library ( Support android4.4 version ) , so I built the project were changed to use api19 . But the phone is android4.1 version . Cause not match .
so low after changed version api, mobile phones can be matched
attached screenshot new project :


------ For reference only ---------------------------------- -----
Thank you both . The average score has been given to you both