Share Point Online listservice Server was unable to process request. ---> Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))

I am facing error while invoking Lists.asmx

 Server was unable to process request. ---> Access is denied. (Exception from HRESULT: 0x80070005 (E_ACCESSDENIED))

It was running in production previously but suddenly it stop working and giving me access denied error

I check all permissions and fedauth is working properly.

  string authCookie = onlineCredentials.GetAuthenticationCookie(siteUri);

            CookieContainer GetCookieContainer = new CookieContainer();
            string trimmedCookie = authCookie.TrimStart("SPOIDCRL=".ToCharArray());
            GetCookieContainer.Add(new Cookie("FedAuth", trimmedCookie, string.Empty, siteUri.Authority));

code example is attached.

            spWebLists.Lists listService = new spWebLists.Lists();
            listService.CookieContainer = cookieContainer;
            listService.Url = url + "/_vti_bin/Lists.asmx";



            listName = "Custom1";
            // Instantiate an XmlDocument object
            System.Xml.XmlDocument xmlDoc = new System.Xml.XmlDocument();
            System.Xml.XmlElement query = xmlDoc.CreateElement("Query");
            System.Xml.XmlElement viewFields = xmlDoc.CreateElement("ViewFields");
            System.Xml.XmlElement queryOptions = xmlDoc.CreateElement("QueryOptions");

            System.Xml.XmlNode node1 = listService.GetList(listName);