If you are using Radiator and trying to configure TACACS on a Dell/EMC switch
You may be running into an issue where it's not dropping you into the sysadmin
group and only dropping you into netoperator (default privilege 0)

The documentation is not especially clear on this issue but what you need to do
is include the "shell:roles=sysadmin" in the initial authorization reply in your
ServerTACACSPLUS definition

AuthorizeGroup admin permit service=ppp protocol=ip {shell:roles=sysadmin}

You don't appear to need the suggested Dell-Group-Name VSA for TACACS - the above role seems to cover it. you can use sysadmin, secadmin, netadmin or netoperator.

the configuration on the switch will look something like (this has tacacs only for remote authentication, and using local users for console logins)

aaa authentication login default group tacacs+ local
aaa authentication login console local
aaa accounting commands all default stop-only logging  group tacacs+
aaa accounting exec default start-stop logging  group tacacs+
aaa authorization commands role sysadmin default group tacacs+
aaa authorization commands role secadmin default group tacacs+
aaa authorization commands role netadmin default group tacacs+
aaa authorization commands role netoperator default group tacacs+

Dell documentation is here : 
Dell OS10 Users Guide 10.5.3