Hi Bill - welcome to the forums. When the rollover switches are closed, even very briefly, the 50 pt relay should energize, and there is a normally open switch on the 50 pt relay that should close and keep the 50 pt relay energized until the score motor has run - a locking switch. (Another switch on the 50 pt relay activates the score motor) Near the end of the score motor's movement, a switch on the score motor (5C) that is in series with that locking relay will open, thus de-energizing the 50 pt relay. (See the snippet below)
Check to see that the score motor is running, when you hit a rollover, and check to see that the 50 pt relay is energizing. If that relay is energizing, that locking switch should activate practically immediately, and the relay should stay on. If it's not doing that, you may have a problem with that locking switch. Use the wire colors on the schematic (looks like blue-yellow and red-green) to identify which switch it is. Clean the contacts of that switch and make sure the gap between the contacts is correct so that the contacts press together and actually slide against each other a bit when the relay is energized. Do the same for all the switches on that 50 pt relay while you're there....carefully.