If your HPE OfficeConnect 1910-48G (JE009A) has been reverted by you to its default...why do you think your Switch hasn't (at least) the local admin user configured by default?
That default admin user has for sure no password set yet...so you should be able to Login into the Switch CLI (via Telnet) because you have full credentials to do so (Login: admin Password: None)...and then you will be able to execute the undo password-recovery enable command only once you entered the system-view mode (that's another story).
It should work that way.
