A prop written with a : reads a value from the document's frontmatter or meta, or a JSON literal. If the path is undefined, the prop has no value. Fix the path or write the prop directly. Bindings to data.* and inherited props.* resolve when rendering, so they aren't reported as undefined while parsing.
Incorrect
To
---
old: log in
---
To :suggestion[sign in]{:from="frontmatter.original"}, enter your email.Correct
To
---
old: log in
---
To :suggestion[sign in]{:from="frontmatter.old"}, enter your email.