An issue arrises when a domain's A record resolution is attempted before Route53 publishes the clusters A record and the NXDOMAIN response is cached in the NCACHE (RFC2308) making resolution impossible until the negative caching TTL expires. These TTLs are typically large enough to disrupt the installation experience. The current workaround is to ensure your TTLs are set to a low interval, or wait for them to expire, then proceed with the installation.
When copying your license and pull-secret from account.coreos.com be sure to choose the correct format. The license format should be "Raw Format", the pull-secret should be the "dockercfg" format.