403 error

Hello,

After a year without probles I get an 403 error when trying to activate a license. I didn’t change any code allthought plugins have been updated.
Activation still works when i use the url in the browser and log in with the consumer key and the consumer secret

I use the following code:

im client As HttpClient = New HttpClient()

        ' Set the base address of the API
        client.BaseAddress = New Uri("https://financialdecisionsupport.nl/wp-json/dlm/v1/")
        ' Set the authorization header
        client.DefaultRequestHeaders.Authorization =
            New AuthenticationHeaderValue("Basic",
                                      Convert.ToBase64String(Encoding.ASCII.GetBytes("ck_xxxxx:cs_yyyyy")))
        ' Set the security protocol explicitly
        ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12
        ' Send the GET request
        Dim response As HttpResponseMessage = client.GetAsync("licenses/activate/" & lsLicenseKey).Result
        ' Check if the request was successful
        If response.IsSuccessStatusCode Then

As a result I get 

-		response	{StatusCode: 403, ReasonPhrase: 'Forbidden', Version: 1.1, Content: System.Net.Http.StreamContent, Headers:
{
  Cache-Control: no-cache
  Content-Length: 93
  Content-Type: text/html
}}	System.Net.Http.HttpResponseMessage
+		Content	{System.Net.Http.StreamContent}	System.Net.Http.HttpContent {System.Net.Http.StreamContent}
+		Headers	{Cache-Control: no-cache
}	System.Net.Http.Headers.HttpResponseHeaders
		IsSuccessStatusCode	False	Boolean
		ReasonPhrase	"Forbidden"	String
+		RequestMessage	{Method: GET, RequestUri: 'https://financialdecisionsupport.nl/wp-json/dlm/v1/licenses/activate/TCCSCC-7G4U-JX5B-LKJLJKJL', Version: 1.1, Content: <null>, Headers:
{
  Authorization: Basic xxxxyyyyyyy
}}	System.Net.Http.HttpRequestMessage
		StatusCode	Forbidden {403}	System.Net.HttpStatusCode
+		Version	{1.1}	System.Version
+		Shared members		
+		Non-Public members	


Any idea how to solve this?