Subdomains cannot be created from command line when Retain web and traffic statistics option in Tools&Settings > Server Statistics Settings is set to any value more than 3:
# plesk bin subdomain --create subdomain -d example.com -php true
An error occurred during domain creation: Unable to accept the template: the following limitations are exceeded.
Description Requested Allowed
Retain web and traffic statistics 3 12
However, creating subdomain from the Plesk control panel (UI) is possible without any error.
This is Plesk internal issue with ID #PPPM-5727, which is planned to be fixed in future Plesk updates.
As a workaround, create subdomain from UI: Domains > example.com > Create subdomain