Hello, there is a bug in the command blocks where if you add delay with ticks, the command is not activated.
I have commands with a delay of 100 ticks and they are not being activated, but with 0 delay, yes.
Linked issues
duplicates 1
Comments 2
This is intentional, see MCPE-145283.
Specifically, command blocks with delayed ticks will only work if still powered when the command would execute. If a command were delayed to 15s after redstone is activated, and on the 10s mark the redstone signal was removed, it would not go off. In previous versions, so long as the command block received any redstone at all, whether it was for the entire duration or not, the command would still fire.