That's a breaking change in Primefaces 10, caused by the fix for issue #6563 which introduces this new validation error: https://github.com/primefaces/primefaces/issues/6563

Suggested changes are:

• Adding attribute: columns="1"
• Adding child tag: <p:row rendered="false"/>

See also: https://github.com/primefaces/primefaces/issues/7272