I think it's a member variable reference error.

[Seungup]

https://github.com/gamestdio/three-text2d/blob/812e35c864767a7c95c6231236b9803dda258da8/src/Text2D.ts#L68

The member variable defineded to

protected _text: string;

but the actual constructor puts the value on

this.text = text;