Command Block input is turned into #######

I was trying to set up command blocks to get to the Nether Fortress. But this video shows why I couldn't.I have 2 other command blocks in the realm, they work just fine, but this one doesn't.

 

https://drive.google.com/file/d/1YArs-Z4thC_VngELZHQ815f-nW3ptict/view?usp=sharing