"It looks like this is not working."
In this sentence you say that it seems to you like this, but you are not sure. You imply here that you might be wrong here.
"Apparently this is not working."
This is a more certain statement. I would say it is equal to saying "As we can see, this is not working."
"This is obviously not working."
This is an absolutely certain statement, saying: "This is not working, everyone can clearly see this."