Thank you for reporting the issue. I see a crash report in the Play Store developer console. I will investigate it tonight (US west coast). Sorry for the trouble.
During my workday I don't have access to the source code, so I don't know what the exact issue is. But can you tell me if you have given the program the permissions (access to location and to shared storage)? The app never shares your location with anyone, and only looks at files in /CustomMaps folder on the shared storage. Also, do you have any previously created maps on your shared storage?
If this prevents you from using the app and you really need it before I can get a fix out, you can uninstall the beta, leave the Custom Maps beta program, and re-install the release version.