Could you please clarify if you have enabled at least one authorization method on the remote Host and set the password for this method? If no authorization method is enabled, you will not be able to connect to this Host as there are no technical, blank or default passwords for security reasons. Here's a relatable Documentation article that might be helpful: https://www.remoteutilities.com/support/docs/security/
Please let me know if there is any authorization method enabled and the password is set but the issue still persists.
I'm so sorry for wasting time here - having used alternate software, I just assumed something would be in place by default. Perhaps it would be good if the software prompted "you've not selected any authorisation method - nobody will be able to connect until you do so" before closing the install. Just an idea.
I've gone back, as you clearly explained, and now selected simple password. Thank you - funnily enough it now works!