I am no expert but have learned a few things
check your yaml front matter with this tool
https://nodeca.github.io/js-yaml/
if it says “expected a single document in the stream, but found more”
Your yaml is valid, otherwise your yaml is invalid.
like this is valid
Valid:
---
language: 
- en
- zh
tags:
- translation
license: apache-2.0
---
### My fancy model

No spaces before tags (like “-zh”) will make this invalid.
More to come as I learn more!
Also the website takes 3 minutes for new tags to be reflected.