This question was asked: https://vexforum.com/t/answered-robots-not-starting-matches-within-size/45803/1
There are potentially two solutions found in the rules:
<G3> At the beginning of a Match, each Robot must be smaller than a volume of 18” (457.2 mm) long by 18” (457.2 mm) wide by 18” (457.2 mm) tall. An offending Robot will be removed from the match at the Head Referee’s discretion.
If there is a need to re-position the robot then here is another rule to consider:
<G7> During the qualification rounds, the red Alliance has the right to place its Robots on the field last. During the elimination rounds, the higher seeded Alliance has the right to place its Robots on the field last. Once a T eam has placed its Robot on the field, its position cannot be readjusted prior to the M atch . A T eam that violates this rule will have its robots randomly repositioned by the referees.
Robots must be placed on the field promptly. Repeated failure to do so could result in a violation of <G1>