SSL Certificate error when accessing API from IBM i

We're getting the error below when we try to connect to an external API from the IBM i.  We were previously able to connect to it without error and without downloading anything to the IBM i or installing anything with DCM.  The API provider created a new certificate and now we get this.  Does anybody have any idea what can be done to resolve it?
com.pjx.cfo.multicast.MulticastException: javax.net.ssl.SSLHandshakeException: com.ibm.jsse2.util.ValidatorException: PKIX path building failed: com.ibm.security.cert.IBMCertPathBuilderException: unable to find valid certification path to requested target at com.pjx.xaf.multicast.handler.HttpHandler.sendMessageProtected(HttpHandler.java:158) at com.pjx.xaf.multicast.handler.AbstractHandler.sendMessage(AbstractHandler.java:168) at com.pjx.slo.SLOServerProcessor.resendMessage(SLOServerProcessor.java:388) at com.pjx.slo.SLOServerProcessor.processMessage(SLOServerProcessor.java:217) at com.pjx.slo.SLOServerProcessor.processMessages(SLOServerProcessor.java:163) at com.pjx.slo.SLOServerProcessor.run(SLOServerProcessor.java:105) at java.lang.Thread.run(Thread.java:825)
Thanks,
Nick