I know I've seen a lot of people post about this, but I've tried the solutions given and it's still not working.

I've checked the "Yes, this is a casting class" box, I've listed it as "spellcasting" in the subclass features, I've set the spellcasting parameters, I've saved everything individually and collectively, and have waited the extra 15-20 minutes after saving before checking on it in a character sheet. It still doesn't come up.

The weird thing is that it shows up in the "optional feature manager" drop down of the class, but it never shows up in the main class feature drop down. The other aspects of the subclass do (as well as on the character sheet), but for some reason this one doesn't. Nor does it show up in any capacity on the actual character sheet.

I'm not exactly sure what the issue is here and I'm not sure what to do about it. Is the best option just to manually punch in the spells available to the class?

You must have made “Spellcasting” as an Additional/Replacement feature. It must be a “Granted” feature. I explained it with details and an image here:

https://www.dndbeyond.com/forums/dungeons-dragons-discussion/homebrew-house-rules/119032-how-to-add-spellcasting-to-subclasses-for

If you have any questions ask me there.👆

That was totally it--thank you so much!