Switching a CM400 modem from Spectrum to WOW!

I've switched service providers. A Netgear CM400 modem that I used with Spectrum for years does not work with WOW! From what I gather, the issue has to do with Spectrum's firmware updates and locking the modem into IPv6.  I've done a number of factory resets, but the WOW! technician still can't connect the modem to WOW!  What can be done to get the modem to work with WOW!? Please advise.