Nunezxmx-- It could be the handle.
Try watching the flapper when you press the handle down.
Some handles sometimes have plastic parts inside them that break so even though the handle may move on the outside, the inner part that grabs and is supposed to make the chain lift does not grab. I had that happen with the lever on my toilet.
Try manually pulling up on the chain to lift the flapper to see if that makes it flush properly, then examine the lever. Does it feel more loose than it used to?