In the following path
programming_fundamentals/rest_part_1/curl_examples.sh
go to the last line and put this:
https://sandbox-iosxe-recomm-1.cisco.com/restconf/data/ietf-interfaces:interfaces/interface=GigabitEthernet2

The host name has been changed for the sandbox in question, hence the above change
CSR1000V Host: sandbox-iosxe-recomm-1.cisco.com