There were server issues yesterday at Galaxy Main https://usegalaxy.org leading to server-side errors (across tools), and more work has been occurring overnight and continues through now. Meaning: even jobs successfully submitted may fail for server-side reasons, or have an extended queue time then eventually fail. It is best to wait a bit for that process to complete before rerunning.
We are investigating whether the problem with RNA-Star not locating indexed reference genomes is related or not.
After searching for a workaround, the reference genomes can be accessed in RNA STAR versions 2.5.2b-0 and 2.6.0b-1, but not 2.7.2b. Hopefully this helps debugging the issue.
The most current version of the tool has more reference genomes added at UseGalaxy.org: RNA STAR Gapped-read mapper for RNA-seq data (Galaxy Version 2.7.5b)