Can not get refresh token

Can not get refresh token

Hi all,
I used this link to get token:
with scope: ZohoCRM.modules.all
https://accounts.zoho.com/oauth/v2/token?code={grant_token}&redirect_uri={redirect_uri}&client_id={client_id}&client_secret={client_secret}&grant_type=authorization_code

But it show: Server error occurred

pl help me this problem.
Many thanks.