Can't sign in to my Apple account on the web

if the problem is that the code never shows up: on your iphone go to Settings > your name > Sign-In & Security > Two-Factor Authentication > Get Verification Code. it works even when nothing popped up. and check the date and time on the computer is right. a clock that's off can make sign in fail for no clear reason.

Does it fail on the password, or after you enter the code? If it's after the code, it's usually the browser. Try a private window with extensions off, or a different browser entirely. Ad blockers and strict cookie settings break Apple's sign-in page more than you'd expect. If it's saying the password is wrong but it works on your phone, the account may be locked for security. Apple's account recovery page will tell you that, and it's the quickest way to unlock it.