Some possible reasons and solutions
Wrong host
Use the “-h” flag:
psql -h localhost -U phisaver --password
Wrong syntax
Use -U and -W flags for user and password
psql -U fred -W
> prompts for password
Not allowed
Check your conf file/s. Google dat.
Ensure TCP access is allowed for remote access, as local Unix socket access is the default.
Admin account
I get password failure with:
psql -h localhost -U phisaver --password
And instead need to switch to the user in shell to execute psql
sudo -u postgres psql
psql>
Finally
Maybe you get a ‘peer authentication’ failure, which means psql is asking the OS to authenticate. Edit /etc/postgresql/12/main/pg_hba.conf and change ‘local’ connections from ‘peer’ (the default) to ‘md5’