I made a homebrew subclass from scratch and it says "This homebrew Subclass does not have the necessary class features with the correct required levels." when I have features at 2,6,10,14.

You can re-create this by making a new homebrew copy of an existing subclass (I tested with Circle of Dreams). It prints the same message at the top.

Need a 3th level trait as the standard subclass is the Circle of the Land.

Are you talking about circle spells? Just adding a feature at level 3 didn't work.

This is what my feature table looks like:

That also seems like a bad requirement as the table doesn't list getting a circle feature at 3rd level and half the circles (moon, dreams, and shepherd) do not have any 3rd level features.

I figured it out. I needed to select WIS in the spellcasting ability box. Seems like it should default to WIS for druid or have a required warning.