Itgenobr019 on use of headless OAuth on Exact Online

Questions
1

When running Invantive Data Hub using 20.1.517 with Implicit Grant Flow, an error occurs:

itgenobr019: A connection to the database ‘…’ could not be established as user ‘…’.
Could not log on to Exact Online using user name and password. Reason is unknown.

Instructions have been followed as given on Circumvent two-step verification and refresh tokens on Exact Online using Data Hub

The HTML found in trace contains text below.

How can I activate the Implicit Grant Flow with Data Hub?

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2

Releases from 20.1.526 onward better show the actual text of the error message. Which in this case reads:

Error itgenobr111: A connection to the database ‘L120\invoicing3’ could not be established as user ‘’.
De ingevoerde verificatiecode is onjuist of verlopen. Probeer het nog een keer. U kunt het nog 8 keer proberen. Daarna wordt uw account tijdelijk (5 minuten) geblokkeerd.

Apparently, not the correct secret key for TOTP was used.

Other possible messages are:

Error itgenobr112: A connection to the database ‘L120\invoicing3’ could not be established as user ‘’.
Het inloggen is mislukt. Controleer uw gebruikersnaam en wachtwoord. Let op: uw gebruikersnaam en e-mailadres kunnen hetzelfde zijn. Na 5 mislukte pogingen wordt uw gebruikersaccount voor ten minste 5 minuten geblokkeerd.

Other error codes are itgenobr108 and itgenobr109.