How should we be able to help if you don’t provide the information being asked in your post ???
If it is an openhabian install, user and password is openhabian unless you changed it.
Default password was not changed. It seems that username/password are not matching. I receive message that password is incorrect.
Is it any manual workaround to restore default credentials?
In case you have root access you can use the root user to change openhabian user’s password.
In case you don’t have root access you can mount the SD card using e.g. a linux life system or a linux rescue system on an other computer. Then change the password entry in /etc/shadow on the SD card.
If they are not matching any more, the default value is not valid any longer then the password was changed.