Please check in the box as shown in the image below:
Then click Aceptar. I believe you just updated to a newer version of Test.Lab and first time launching the software? I believe it's warning message from your PC, that warns you about the .lms file extension which it's the LMS project file. Nothing need to be concern here. If you do not check the box, next time launching Test.Lab same warning message will pop up, until you check the box.