Make sure the data was completely loaded into Galaxy (check size of uploaded file versus the Galaxy dataset), that the datatype "vcf" is assigned, and the metadata is intact (no yellow "warning" in the dataset's expanded box in the history).
If you haven't run any tools with it yet, give that a try. Or if you had prior problems, re-run now to see what the results are. There are many tool choices in the group "VCF Manipulation". Run a few if you encounter errors since some have more descriptive error messages than others.
If you cannot determine the problem from an error (if any come up), a bug report can be sent in if working at http://usegalaxy.org or if the problem can be reproduced there.
When reporting a bug that has an associated Biostar post, include a link to the post in the comments. And be sure to leave the datasets undeleted for the best feedback (inputs and outputs). https://wiki.galaxyproject.org/Support#Reporting_tool_errors
Thanks, Jen, Galaxy team