Problems with uploading images

I tried adding a humorous meme to a recent post (yet another F-34T one), but it came up with the error message "You do not have permission to add images to posts." Not "Invalid file type" or anything, just "no permission." Why? 

In addition, when I tried posting a verbal response instead, it said “Maximum posts reached” or something approximating that, and wouldn’t let me post. Reloading the page didn’t work, it just autofilled what I’d previously written, so I had to close the tab entirely.

And THEN, when I tried making this post, it came up with the same “maximum posts” nonsense, and auto saved whenever I tried to reload or even make a new topic. I had to switch to my phone just to make this.