How to center text under image?

For site https://www.musicminister.net Catch Flames FREE theme After update in late 2019 I could no longer center the text that appears under an inserted image. I can still center the image itself, but the text under it lines up with the left edge of the image, and is not centered under the image. Used to work, but not now. Also, though text WAS centered in older posts, the theme update changed all those, too. Captions under images now line up with the left edge of the (centered) image, but not centered under the image. Help, please? THANKS!!! :-) -Dale