Always choose
"Screen Space - Overlay"
and
"Scale with screen size"
It's just one of those weird things about Unity ... 99.9% of the time you use that setting.
In the current version of Unity, Unity screwed-up and set the default wrong.
Only in extremely obscure situations would you use the other settings: it's a huge source of confusion that Unity have the defaults as the wrong settings.
You could have another problem but be sure to do that.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…