This means that the circuit breaker for the vacuum pump has tripped, this is normally due to the vacuum pump drawing too much current, but could also be because of a power surge or other anomaly.
The oil should be checked in the vacuum pump to be sure that it is clean and completely filled. Once this is verified the circuit breaker in the main electrical cabinet can be reset and the pump can be turned back on.
If the breaker continues to trip the current draw of the vacuum pump should be measured. On some systems the vacuum pump circuit breaker will have a variable amperage dial. In this case the allowable amperage can be increased to account for a small increase in current draw as the pump ages.