With the recent updates to Google's policies in regards to 3rd party apps hubsell has to change the way it is connecting with your mailbox.

In order to whitelist the hubsell app, the g-suite administrator of your organization should follow the instructions at the following link :

https://support.google.com/a/answer/7281227?hl=en

https://admin.google.com/ac/owl/list?tab=configuredApps

If the g-suite administrator is asked for the "client id" of hubsell you'll find it on hubsell's "my profile" page, on google row.

Here is hubsell's client id: