i have this problem and i fix it as following :
go to this path where ur wplsoft simulator installed:
C:\Program Files (x86)\Delta Industrial Automation\WPLSoft 2.49\Simulator
then right-click on ur plc type simulator: for example, mine was DVPSimulator_SS2
on compatibility tab >>>>check ur windows: I changed mine to windows7
>>>>>check if in ur privilege level the administrator permission is given.
Click on apply and reopen the wplsoft.