How to Debug this Text Error

I get this error with my texts:
Failed to update dynamic font (SigmarOne-Regular) texture; all the needed characters do not fit onto a single texture (max size 4096). Try using less text or a smaller font size.
UnityEngine.Canvas:SendWillRenderCanvases ()

How do I know where it’s coming from?

Sounds like maybe a TextMeshPRO error? If you’re using TMPro, try striking the font at a smaller size perhaps.