What should a man do who is meticulously monitoring a machine and cannot leave it at prayer time except with a substitute, and is he required to change his job because he misses congregational prayers?

Performing congregational prayer is obligatory for a man who is able, and falling behind from it is a characteristic of the hypocrites, unless there is a valid excuse.

Scholars have mentioned that fear for one's private property or the property of others, or for one's livelihood which a person needs, are among the excuses that permit missing congregational prayer. This includes fear of financial loss or damage to property, or fear for property entrusted for safekeeping.

Based on this, there is no sin upon the questioner for missing the congregation to monitor the machine, with the caveat that it is not permissible to be totally preoccupied from prayer until its time has expired.