USB network connection TP-Link-AC1200-Archer C5

I can't get a USB network connection with the TP-Link-AC1200-Archer C5 in my laptop (Lenovo, Linux Mint). In the Nenovo with a new folder and "Connect server", the connection is always terminated directly. The LUCI system log says "authpriv.info dropbear [7308]: Exit (root): Disconnect received"! Is a key missing?
With SSH I get into the mountpoint folder.
What can I do?

I'd say you need to follow https://openwrt.org/docs/guide-user/services/nas/sftp.server

Hallo Mr. Maurer,
A connection to my laptop now works with sftp. But I want to connect to
my mounted USB stick (NAS).
This is / srv / usbstick. Which config has to be changed there?
Many Thanks!

greetings
Norbert

then you need to follow https://openwrt.org/docs/guide-user/services/nas/samba or better (if running linux on the laptop) https://openwrt.org/docs/guide-user/services/nas/nfs.server