So I've tried to make it work by either putting commands after or before the block or even no commands at all other than the set size to block. I'v also tried the Change size by block but that doesn't work either. I'v checked with all my other friends who do scratch and they have the same problem. Can someone help me use the size blocks correctly? Because of this problem I'v had a hard time working on different kinds of projects and it's starting to get annoying. I'm not sure if this was already a post but if it was I didn't see it anywhere.

Share your project. Sprites have different maximum sizes you could already be at max. But we need to see the sprite in question to help

mstone326 wrote:

Share your project. Sprites have different maximum sizes you could already be at max. But we need to see the sprite in question to help

So I did. here is the link: https://scratch.mit.edu/projects/553861091

The fix might seem a bit weird, but it is needed - go to the sprite which needs to be fixed, and go into the costume editor.
Notice that the costume is listed with a large resolution such as this:

The thumbnail also shows that the actual costume you want is tiny - this is because Scratch thinks the costume is way bigger than it actually is.
To fix this the costume needs to be updated.
It's up to you with how this can be done. Just select the eraser tool and try erasing the blank part of the costume. The dimensions will update. Now try running the set size block again.

Thank you @awsome-llama!