error 1055 "Error 1055 occurred at Property Node in niFpgaGetTargetClassFromTarget.vi:6910002- >niFpgaDEN_Execute.vi:32001- >Testbench_base.vi Possible Reason(s): LabVIEW:( hex 0x41F) Object reference is invalid"

[Matteo.T]

HI there, i am using LabView2018 since a couple of months for my master thesis, so i am not  an expert. I am co-simulating Labview and Multisim and simulating an FPGA target on Desktop with the " Desktop Execution Node". I am always encountering this error " Error 1055 occurred at Property Node in niFpgaGetTargetClassFromTarget.vi:6910002- >niFpgaDEN_Execute.vi:32001- >Testbench_base.vi    Possible Reason(s): LabVIEW:( hex 0x41F) Object reference is invalid" after lot of minutes of simulation. I could't figure out the reason why it appears only after lot of time the start of the simulation and i have no idea how to fix it. I would be very glad if anyone had a suggestion. Thanks in advanced!