I've created several homebrew subclasses at this point, but this is the first time I've had this problem.  I was making an illusion-based sorcerer class based on the mesmer class from Guild Wars 2.  I selected the Aberrant Mind subclass template and made changes to everything from the description to the abilities and spells.  However, it still won't let me publish it due to it being 'too similar' to the Abberant Mind subclass.  I played around with everything I could and it simply wouldn't let me upload it. 

So I created a sorcerer subclass from scratch.  I copy/pasted all of the information I had already entered into it and made sure all the class features were granted at the appropriate levels.  However, it is now telling me that not only are the class features granted at the incorrect levels, but that the subclass is somehow too similar to the Circle of Spores druid subclass, despite being a sorcerer subclass.

Has anybody been having trouble creating subclasses lately or encounter a similar problem?

Two things:

1) the compliance checks are only run when you save from the save button in the topmost section (basic I formation, or a similar name)

2j the circle of spores warning usually means you don’t have a long enough description in the description box. 

In addition to what ArwensDaughter wrote, you can find answers regarding other error messages and a whole slew of other stuff in the homebrew FAQ: (https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/131411-a-homebrewers-how-to-faq).