ns2 are usually used for DNS nameservers, not for websites. Are you certain the addresses are your dedicated web-server addresses?
I would expect you to to set up at Godaddy a name like
www.mysite.tw with an address like
Either you typed something other than just
www.mysite.tw or Godaddy are not aware of the tw top level domain (TLD) - which seems unlikely if you registered
mydomain.tw with them.
www.mysite.tw - if that gives the same error message, I would call/email Godadady support for assistance.
If the hosting company want you to get mysite.tw delegated to their nameservers, you can check the situation as follows:
C:\>nslookup -type=NS facebook.com
facebook.com nameserver = ns3.facebook.com
facebook.com nameserver = ns4.facebook.com
facebook.com nameserver = ns5.facebook.com
facebook.com nameserver = ns1.facebook.com
facebook.com nameserver = ns2.facebook.com
ns1.facebook.com internet address = 126.96.36.199
ns2.facebook.com internet address = 188.8.131.52
ns3.facebook.com internet address = 184.108.40.206
ns4.facebook.com internet address = 220.127.116.11
ns5.facebook.com internet address = 18.104.22.168
Just substitute mysite.tw for facebook.com in the above command. It will show you that Godaddy's nameservers are managing the mysite.tw domain.
I don't use Godaddy so I don't know if you can arrange this delegation using their control panel, more likely you'd have to ask Godaddy to do this for you.
After Godaddy say they have delegated nameservice to your hosting company, run the above command again to see that the change has occurred. You will need to wait for the DNS cache period to expire.
This delegation seems unnecessary to me. I would expect you just need to discover the IP-address of the web-server hosting your site and use Godaddy's control panel to set up a DNS "A" record for www.mysite.tw pointing to that IP-address.