So this probably doesn't have anything to do with the screens.rpy file if you didn't change it. Instead, I'd venture to guess whatever you just changed is the issue and renpy is just giving you an unclear error message. Can you remember what you were doing when this issue popped up?
It's also probably got something to do with what you wrote in the script since (im no expert but) indentation mismatch seems to imply what you wrote in your script isn't in the same format as how screens.rpy intended it to be.
Say I had a format that went a little like this
Screen lildickies ("user_input1", "user_input2"):
textbutton user_input1 action (Hide("lildickies"), Jump(user_input2)):
What this format is doing here is it's defining "lildickies".
The first line dictates how lildickies will be used in script.rpy.
The second line dictates what lildickies will do after it's used in script.rpy
How this particular format called lildickies would be used in script.rpy is like this
Show screen lildickies("Continue", "secondlabel")
It would then look a little something like this
Pressing that button would then jump to label "secondlabel" in the script.
Why I'm telling you this is, because most things you see in the game are made with these screens.rpy formats that includes the "say" format.
Whenever you write into your script something like
You may not realise it, but that right there is using the "say" format from the screens.rpy file. It's a specific way of writing something in the script where renpy will automatically realise "oh ok. They're trying to use the 'say' format".
Now what I think you've done wrong here is, you've written in your script.rpy, some bit of code that has too many spaces before it. Like for example,
This wouldn't work
But this would
Holy shit, let it never be said I didn't try to help here.