Java SDK - Invalid Response

I’ve written an implementation using the java SDK at https://github.com/mlbiam/unison-auth-duo/blob/master/src/main/java/com/tremolosecurity/proxy/auth/DuoSecLogin.java and am running into issues validating the app response. The auth response runs fine. I was also able to use the demo app without issue. Have triple checked the various parameters. How do I go about debugging this? Here’s the stack trace:

Caused by: com.duosecurity.duoweb.DuoWebException: Invalid response
at com.duosecurity.duoweb.DuoWeb.parseVals(DuoWeb.java:109) ~[unison-auth-duo-1.0.17.jar:?]
at com.duosecurity.duoweb.DuoWeb.verifyResponse(DuoWeb.java:74) ~[unison-auth-duo-1.0.17.jar:?]
at com.duosecurity.duoweb.DuoWeb.verifyResponse(DuoWeb.java:61) ~[unison-auth-duo-1.0.17.jar:?]
at com.tremolosecurity.proxy.auth.DuoSecLogin.doPost(DuoSecLogin.java:106) ~[unison-auth-duo-1.0.17.jar:?]
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