I reset the plugin in case a config was the issue, but whenever I place an enchantable item in the table, none of the enchantments show up. I can only enchant using commands. This isn't much of an issue for myself (server admin), but I'm sure my players will be annoyed.
Server is spigot on 1.14.4
Any ideas on what's causing this issue or how to fix it?

This seems to be a bug which occurs in newer Minecraft/Spigot versions and can temporarily be fixed by modifying the enchanting inventory. (e.g. removing items and putting items back in)
You could try out the newest version and report back if this still doesn't work for you.