Authorization issue with SAP DropBox Adapter

[seb-g]

Hello,

I have copied the DropBox adapter provided by SAP in the content discovery, and followed the documentation.

However, when trying to authorize the OAuth2 Authorization Code from the "Monitor->Security", I receive the following error back.

[OAuthCodeCredentialManagement][OAUTH][ProblemDuringCallingTokenEndpointWithCode]:Problem during calling the token endpoint of OAuth2 Authorization Code Credential "DropBox" with grant type authorization_code: Problem during requesting the refresh token for the OAuth2 Authorization Code Credential DropBox: javax.net.ssl.SSLException: MAC values do not match

I have already tried to add the DropBox certificates chain, it doesn't help. 

Other OAuth2 credentials are working fine.

Any idea what could be the root cause ?

Thanks