I replace a manual thermostat with a digital one and now it want turn on the a/c

Did you check all the obvious things, like the batteries, return power to unit at breaker, set the time and the temp settings ? Sometimes the default program has the temp at a different setting than you want and you need to override it with a manual setting. Even the new batteries you installed in the thermostat might be dead. Anyway, since its a new unit, somewhere on the package is a web site address for technical help. If you've done everything per instructions, then they would be the best place to contact.