after ugprading to ubuntu 20, the nas is no more work. It show the error message like „Software caused connection abort“.

Why? Becuase in ubuntu 20 is samba not more installed at default. So you need to install it first.

apt-get install samba

After that you need to change the config, add support for „old samba protocol“

Add „client min protocol = CORE“ in Seciton „[global]„

Thats all.