black screen, doesn't recognize password.

Do you use an encrypted file system ?

No, is not encrypted.

No, is not encrypted.

Apparently there are different issues:

1. The graphical GUI seems not to start correctly.

2. You get the command line environment, but you have problems with your password.

Which Ubuntu release are you running?
What kind of update do you run, which then caused that problem?

Do you use a non-English keyboard and have special characters in your password? Maybe the system is interpreting the keys in a wrong way. In that case you could try locating the special keys o an English keyboard and pressing these key instead (if that is possible at all).

Thank you for concerns! I installed Ubuntu 17.04 last year. From time to time system advises me for updates, and that was the last issue few days ago. After L placed password it start download and installed all of them. Had to restart it, but is not recognizing same password. I am using wifi keyboard, and had no problems with it so far. Hope this will help. Thank you.

Actually, is not writing any letters or numbers when tape them for password.

Thanks actionparsnip, that solved my question.