Server encauntered an unexpected condition that prevented it from fulfiling the request ERROR 500

[partsshop4]

Hello guys, im trying to work out the workflow that would give me the refresh_token and the access_token. I have did everything corretly, the tokens, endpoint, headers and parameters, but i keep getting the same error everytime i try to make the call. What can be causing this problem and how to solve it?

[shipscript]

You'll have to provide a little more info, like which endpoint and some of the code.