Some dwarf stays outside ignoring all my "commands"

I recently started a new fortress. My Mason (a valuable dwarf) is just standing outside during snow storms and stuff with "No job". He doesn't eat and drink.

I tried different stuff to get him back:

• Switched off all his labors (thought he would stuck in a job or somewhat)
• Made a burrow and called all civilians into it
• switched back on his labors (tried to get him a job)
• He could get inside (other dwarfs do so, too)
• He hasn't any injuiry (exception: hungry and thirsty from standing outside :/ ) and hes capable to walk.

Long story short, he died of thirst. But now my expedition leader standing outside too.

Any ideas what i am doing wrong? Thanks!

You must make sure your outside Dwarves are able to enter the fort again. You could check if the "outside" is accessible by building something outside, if it tells you that there isn't material available, your problem is there. You can even track where the problem is using this by moving the cursor along the route you think your Dwarves should be able to access.