Hi,
I'm sure you must have fixed this by now but answering so that others can fix this.
I had been facing this problem whenever I was trying to publish a page along with a NullPointerException in the logs [1]. On further digging, I found that AEM tries to find references for the page, including the configurations inside /etc/cloudservices (and I'm sure there could be more).
In my case, a jcr:content node was missing under one of the configurations which was leading to the NPE and the "Failed to retrieve references.." error. I simply copied a jcr:content node from other configs and removed the unnecessary properties, except the sling:resourceType property and was able to fix the error.
java.lang.NullPointerException: null
at com.day.cq.wcm.webservicesupport.impl.ConfigurationReferenceProvider.findReferences(ConfigurationReferenceProvider.java:86)
at com.day.cq.wcm.core.impl.reference.ActivationReferenceSearchServlet.doGet(ActivationReferenceSearchServlet.java:115)
at org.apache.sling.api.servlets.SlingSafeMethodsServlet.mayService(SlingSafeMethodsServlet.java:269)
at org.apache.sling.api.servlets.SlingSafeMethodsServlet.service(SlingSafeMethodsServlet.java:345)
at org.apache.sling.api.servlets.SlingSafeMethodsServlet.service(SlingSafeMethodsServlet.java:376)