Creating snapshot remotely using ssh

I’m following this guide to remotely backup snapshots:

I’ve got ssh setup without needing a password and can ssh straight into HA, with no problems.
A line in the script that needs to be executed is:
‘ssh hassio ha snapshots new’ (hassiso is the alias for the IP address of HA.)

It appears that ‘ha snapshots new’ is not executed, with the follow error returned:
“time=“2020-06-29T12:51:35+01:00” level=error msg=Unexpected server response”

Does anyone have an idea what may be wrong, please?
Jim