TextMeshPro 3.0 is no longer supported. Please update to 3.2.
Reproduction steps:
1. Open the attached project “TextMeshProFont“
2. Open the Fonts folder “Assets/TextMesh Pro/Fonts”
3. Right-click the Liberation Sans font
4. Create new font Create>TextMesh Pro>FontAsset>SDF
Expected result: New font is created successfully
Actual result: Errors are displayed in the Console Window