I am also having this issue. I am using v3.6.4. Just had a switch that went down and was trying to use this tool to analyze the crash report.
When attempting to use the tool, I am seeing quite a few TCP reset-O's in my firewall logs. Wondering if the service is unavailable? Additionally, I am successful in running the IOS-XE System Diagnostics, but not the IOS-XE Crashinfo Analyzer.