Authorize.net is implementing changes & as a result:
Any customers having the Authorize.net DPM prior to November 10, 2016 for versions 4.4.x through 4.7.x will need to get an updated module before July 19, 2019 according to Authorize.net:
https://developer.authorize.net/api/upgrade_guide/
Anyone running the Authorize.net DPM on 4.0.x through 4.3.x will need to contact us for customization so that their module will continue to work past July 2019.
Please contact us to receive a quote for the update or customization