Dear @Hadi
I see you missed a lot of things in the code you provided. You forgot the OTP part, API url and it looks like your CSR is not in the recommended format. You also didn’t mention what error you are getting.
You can try this code to get CCSID from Sandbox.
curl -X POST ^
-H "Content-Type: application/json" ^
-H "Accept: application/json" ^
-H "Accept-Language: en" ^
-H "OTP: 12345" ^
-H "Accept-Version: V2" ^
-d "{\"csr\":\"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\"}" ^
"https://gw-fatoora.zatca.gov.sa/e-invoicing/developer-portal/compliance"
Hope this helps.