For example, depending on the font:
- the number one and a capital "I" and a lowercase "L" all could look the same.
- the number zero and a capital "O" could look the same
One thing when you enter it "live" is that it may show a "*" as you type in the letters. Sometimes entering in capital letters may cause you problems since you have to engage the SHIFT key. One thing you could try is type/enter the password into a text editor. Ensure it looks correct and copy and paste it in.
Also be sure to clear the copy paste history as needed.