Last month our a/c went out, we had a guy come in to repair, it was the motor and cost about $400 to replace.
Now the a/c won't won't come on at all. We changed the batteries on the thermostat and still nothing.

Does anyone have a guess as to what we could do or what the problem
may be.

Check the electric connection,maybe it is loose.

Check the circuit breakers for both the inside unit and outside unit.

When turning the fan to ON at the thermostat does the fan in the inside unit come on?

we checked the breakers, they are fine. When turning the unit on, nothing happens. We also checked the connections as the firmbeliever suggested and nothing.

We have called someone to come out and are patiently awaiting their arrival.

However, if it's something we can fix on our own we would like to do that.

Some newer units have a fuse on the circuit board in the inside unit. You might check that.