I’ve checked everything, and I’ve tried what I can do.
Even direct connect from runways to those 6 stands. None of them works.
I also checked taxiways, one row, two rows even three rows of taxiways none of them works.
I have no idea why. It keep says Runway Not connected (for Arrival and Departure both)
I’ve tried enter and exit taxiway for each runway but didn’t work. However as DomiWi said, I just turned game off and on again, it worked just fine. Hmm probably it was a glitch.