Hello Umang Shah,
From the 'Account restricted' error for accessing DialogFlow ,it seems the requests didn't reach Dialogflow server.
You may contact the Org Admin to follow the steps described in [1] to enable Google services for the user
If the issue persists :
1) Create a new organizational unit [2]
2) Move the affected user to that organizational unit [3]
3) follow step 5 in documentation [1] to toggle settings for that organizational unit to OFF, then turn ON again to force the flag to update.