Dukane does still manufacture clock systems. The current master clock is model #24A715. The Dukane 24A700B is long out of production, so getting support from UTC is going to be difficult to get.

You can find your local Dukane dealer for help online here: https://wtb.utcfssecurityproducts.com/geswtb/Dispatcher?REQUEST=WTBBASICFILTER

What kind of secondary clocks are you running? Just about any master clock can run just about any model of secondary clocks. You may be better off returning the used Dukane 24A700B and getting a new, currently supported unit from someone else. We often use the model MC41LV from ATS in retrofit situations (https://www.ats-usa.com/overture/master_body.html). It works with a lot of different clock systems.