Thanks so much for posting about this.
There was a bug that hit a few weeks ago that we’ve since resolved. The issue was that you could nest collection lists inside a symbol and drop as many instances of that symbol into one page – the made it possible to add more than 20 collection lists to a page – a strict limitation up until that point.
We were able to resolve this issue which prevents this from happening again, but unfortunately we weren’t able to push a retroactive fix meaning sites that were impacted by this still have the underlying issue.
The solution here is to delete the excess lists. Once you have 20 lists or less, you will be able to add elements to the page as expected.
In your project @smag23 it looks like you may have already done this for the home page. If you are experiencing the issue on another page, I recommend the same solution.
@ROOSTER it looks like this issue is a different one. I’ve broken off your comment to a new topic here: Cannot move collection lists if there are 20 lists on a page