Make sure to disable the "Pause sim if focus lost" option in Prepar3D/FSX.
If the sim is paused (eg because you tab out) it will not send any updates to SPAD.neXt.
If SPAD.neXt does not receive any updates from the sim for 2 minutes it assumes it crashed and will shutdown.
Still working on the backlog of tickets. Please bear with me. If you have a licence-ticket that needs urgent attention update it to push it up.