FYI: I have two adapters showing on my management page because before my retirement I had two Vonage voice lines and a fax line. Depending on how the Vonage CSR setup your new phone number, you may also see two adapters (your old adapter, and a new adapter that hasn't shipped yet). If neither of those pages work for you, you should be able to call the telephone number on the adapter management page (assuming that you have an alternate way to make a telephone call) and provide the current adapter's MAC address to a Vonage tech, who can then manually re-activate it in their system and force the new phone config to it.
One thing else, if you have not already power cycled your Vonage adapter since it stopped working, try that. It has been my experience that after Vonage changes the phone config, the adapter sometimes needs a power cycle to actually activate the changes.--
We can never have enough of nature.
We need to witness our own limits transgressed, and some life pasturing freely where we never wander.