This not at all clear,, are you trying to boot emmc or SD, do you have some boot at all?
Some generalities
1) check that what you are typing is what you are getting, type password in 1st field
Don't hit enter, backspace it away, also check root password
2) if you remember root password, that is the easiest. root can change any password,,
passwd $USER and follow prompts
3) the nuclear option, blank password by editing etc/shadow (on right device)
field separators are ":" (colon),, make 2nd field blank (ordinarily 40-60 chars, hashed password)
as so,,,,,root::more fields OR $USER::more fields
Some generalities
1) check that what you are typing is what you are getting, type password in 1st field
Don't hit enter, backspace it away, also check root password
2) if you remember root password, that is the easiest. root can change any password,,
passwd $USER and follow prompts
3) the nuclear option, blank password by editing etc/shadow (on right device)
field separators are ":" (colon),, make 2nd field blank (ordinarily 40-60 chars, hashed password)
as so,,,,,root::more fields OR $USER::more fields