Hope this will help you: https://kb.juniper.net/InfoCenter/index?page=content&id=KB15725&actp=METADATA
Hope youre doing good.
Please check the following technical documentation and refer the section "Recovering the Root Password for Junos OS Evolved" - https://www.juniper.net/documentation/en_US/junos/topics/topic-map/recovering-root-password.html#jd0e563
Password recovery is same for all the platforms. May be the issue is related to this PR: https://prsearch.juniper.net/InfoCenter/index?page=prcontent&id=PR1381653
No single user mode means most probably you have marked your console as insecure from the configuration.
Do you have the device old RSI or configuration?
If yes, Check for the following command:-
set system ports console insecure
If so you wont be able to recover the same using console boot and the only option to recover is re-install the OS using USB.
the srx just arrive at my office. unable to retrive the previous config. trying the default login but not working at all.
You may have to re-image the box as there is no option to recover the root password in this case. Please refer the following link for the same: https://kb.juniper.net/InfoCenter/index?page=content&id=KB30944&actp=METADATA
What Junos code are you on?
Per the PR suggested up here, PR1381653, the codes this is fixed in are:
Reinstalling the OS would do the trick.
Hope this will help you : https://kb.juniper.net/InfoCenter/index?page=content&id=KB14102