“TranslateApiException: Invalid authentication token. Microsoft DataMarket is retired. Please subscribe to Microsoft Translator, in the Cognitive Services section at https://portal.azure.com. Please visit https://cognitive.uservoice.com/knowledgebase/articles/1128340-announcements-action-required-before-april-30-20 to find detailed instructions. : ID=0824.V2_Soap.GetTranslations.4EEAF6E3”

MAT v4.0.1810.0 (VS 2015 / VS 2013) and v4.0.6810.0 (VS 2017)* contain the required provider update. With this update the Microsoft Translator provider needs to be configured to use your Cognitive Services subscription for proper operation.**

* MAT for VS 2017 installation does not include the editor. Be sure to install the editor from MAT v4.0.1810 if not already installed / upgraded.
** The Microsoft Translator provider no longer provides unlimited access to machine translations.  The free subscription tier continues to be offered for monthly use up to 2 million characters.  See Cognitive Services Pricing for more information about pricing

Connecting the Microsoft Translation provider to The Cognitive Services.

Obtain your Cognitive Services Translator Text key: 
1.  Use this link to create a new Translator Text Key: https://ms.portal.azure.com/#create/Microsoft.CognitiveServicesTextTranslation.
(For details, see: How to sign up for the Translator Text API)

Configuring MAT with the Cognitive Services Key
2.  Open Credential Manager in the Windows Control Panel
3.  Select Windows Credentials
4.  Select Add a generic credential
     - Internet or network address - enter: Multilingual/MicrosoftTranslator
     - User Name – enter: Multilingual App Toolkit
     - Password – enter: <Your authentication key> obtained from Azure.
     - Click Save
Note: When copying and pasting from this page, be sure to remove any trailing spaces that may have been included.

Once completed, the Microsoft Translator provider will use you Azure account to provide Microsoft Translation Services.