The rules for player readiness changed in early 2019 and again in 2020. The USAPA-IFP Rule 4.C. now states that “Any Player may indicate ‘not ready’ prior to the score being called.” In sub-paragraph 4.C.2., the Rule Book goes on to state that “After the start of the score being called, ‘not ready’ signals will be ignored, unless there is a hinder.” ​ In your scenario, a receiver becoming “not ready” was a fault last year, but in 2020, it can be ignored by a referee and a server, although the server does still have 10 seconds to actually serve the ball. Should, as you asked, the referee have given you a warning? Not in 2019 or in 2020. Last year, the referee could assign a fault to the receiving team and in 2020, the referee would simply ignore the receiver’s not ready signal.