I have the exact same issue. No matter what I do, they never come back to life on their own.
i must either rig up an absurd contraption to continuously reset all the command blocks, or I must manually restart all of them.
Logging out and back in doesn’t repair them, the glitch is kept when backing up, so your map will be broken as a result of dead command blocks,
AND WORSE YET, THERE’S NO WAY TO KEEP THEM ALIVE!
I’ve tried Turning off always active and placing a red stone block to power it, it still glitches…
this bug should have been fixed years ago, but it’s still breaking maps including mine and it’s extremely annoying.
Nearly all bugs I encounter when play testing are dead command blocks.
I can only guess that the game realized there’s too many command blocks and tries to optimize by running less of them… BUT THEN IT DOESN’T TURN THEM BACK ON WHEN YOU NEED THEM! It’s extremely annoying!!! I have to run around my entire map manually repairing dead command blocks like an endless stupid game of wackamole!!!!
NOTE IT’S STILL DOING THIS IN THE ABSOLUTE LATEST VERSION 1.20 pre-4
Edit I just noticed this one actually posed from my phone, (my phone was being extremely buggy and I assumed it never posted, so now two posts exist of this same issue.)