Root cause was my AP and Fire HD Tablet. Recently, I upgraded my Internet and changed NAT(AP), too.
Much faster but failed to connect when I tried to use spacedesk app.
I installed back old NAT(Asus AC1900) which was exclusive for tablet and it connected to new NAT.
They(PC and tablet) worked nice as before. Maybe Fire HD WiFi wasn’t compatible with my new AP.
So, the problem was to devices, not Spacedesk.