I was working on a world with command blocks, but while debugging I couldn't seem to get any thing shown in chat. I was assuming I was doing something wrong, and I checked for an hour. Then when I left the world and got back in, I started seeing the debug messages again. I was confused and I was going to continue working, but as soon as I edited that same command block, it stopped showing it again. I even tested with only changing non important things, like the text in the say command, and it still had the same result. I got out of the world, the game, and shut down my device and turned it back off, but it still had the same problem. I was doing this all on my iPhone, so I tested it with a Chromebook, to see if it was a me problem. I did the same thing to check for the problem, and it gave me the same issue.

(I tested it by going near (0, -60, 0), and putting a repeating always true command block, then I typed in "execute if block 0 -60 0 redstone_block run say test", then I would place a Redstone block on those coordinates. After that, if it showed me "[] test" in chat, I would change only the text for the say command inside the command block, then it would stop showing me any text from the command block at all. After that, I would rejoin the world, and it would show it to me again, until I changed the command block again)