home page 404 not found error (spacious theme)

Please help! I’m running the Spacious theme on my business site. Suddenly, my home page displays a 404 not found error. I think it is related to the theme. I was successfully able to add the TG services widget to the 404 not found page, and now it displays at least, but the slider is missing, and it still displays a 404 not found message.

I recently installed the Social Media Feather plugin. I tried deactivating it, but that didn’t help

I am a novice at this, so please post any replies in plain English. If you think what you wrote was easy to understand, dumb it down even more, please!