I've been using Scopus API for a few weeks and it was working perfectly without any problems. but suddenly it stopped working. I thought the quota had been exceeded but when I looked at the HTTP response I saw response code 401 and status of AUTHORIZATION_ERROR.
Then I tested here https://dev.elsevier.com/scopus.html#!/Author_Retrieval/AuthorRetrievalid using the default API key (7f59af901d2d86f78a1fd60c1bf9426a) but it still gave me AUTHORIZATION_ERROR, some of the functions work e.g. Abstract_Retrieval but I need Author_Retrieval and it doesn't work. it's near a week that it is not working.