Android Question ResponseError. Reason: Unauthorized, Response: {"Msg:"Authorization has been denied for this request

I have an HttpJob where I'm trying to set the header in the following way.
While requesting any data from API, the request should include Authorization header with Bearer as its scheme then follow by authentication token.

JobNDLogin.Initialize("JobNDLogin", Me)
JobNDLogin.Download2("https://test.b2b.com.my/api/cust/Login", Array As String("username", strLoginID, "password", strLoginPassword))
JobNDLogin.GetRequest.SetHeader("Authorization : Bearer " , access_token )

I obtain the following error.
ResponseError. Reason: Unauthorized, Response: {"Msg:"Authorization has been denied for this request

Any suggestion to fix this problem?
Thanks a Lot to everyone.
Best regards.