High Volume SMS Stopped Working

Our High Volume SMS app recently stopped working. It has worked for the last couple of years, but recently we get an error when we try to send a batch: "errorCode":"CMN-101","message":"Parameter [from] value is invalid." I get the same error when I try to send from the API documentation page. We have 5 numbers set up with A2PSmsSender to send from, they all used to work and now I cannot send from any of them. Seems something changed on the account, but I cannot figure out what.