Another item to add: The pasword-hash you pasted is not a valid hash string. The password hash must include the hash algorithm number, the salt, optional rounds (for SHA2 hashes), then the hash string.
This is the hash for "vpn123":
$5$WmMWnbdP4tkgqFYF$2K9uRm1mEssDwT6VuEbHDdCvXPWnyjYqOhLrgC22Wu7
So you'd use:
clish -c 'set user admin password-hash $5$WmMWnbdP4tkgqFYF$2K9uRm1mEssDwT6VuEbHDdCvXPWnyjYqOhLrgC22Wu7'
NOTE: You MUST use single-quote characters here, NOT double-quotes!
(if i had a <blink> tag, i'd use that, too)