Could you please try the following steps:
1- Close Reader
2- Hold down Windows key and press R on your keyboard, this will bring up Run dialogue box.
3- Type regedit in the run dialogue box and hit Enter, click Yes when User Account Control pop-up appears.
4- Navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options, delete the key AcroRd32.exe
5- Relaunch Reader