Make sure "spawn-protection" is turned off or is not causing problems.
If you use WorldGuard, allow chest interaction and opening in the region.
Check that no other protection plugins are stopping players from opening the vaults.
Holograms don't spawn
The plugin uses Armor Stands for holograms. Make sure none of your other plugins are blocking entities from spawning. Using entity cleaners is also not a good idea. The most common reason for this problem is WorldGuard stopping the Armor Stands from spawning.
How do I change the holograms?
All settings for holograms are in the vaults.yml file.
Some of the things you can do are:
Completely customize the lines of text.
Make different rules for when to show certain lines.
Choose how often the holograms refresh.
Set how close players need to be to see the holograms.