They replaced the serpentine belt, charged up the battery, but the car will not start?

Hello,

It sounds like when the belt broke it put excessive pressure on the electrical system and probably got a faulty relay.
Check the power distribution relay under the hood (see diagram below).
Test the relay.

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Also look for any burn relays in that junction box as well.
More than likely you had a overload in the system and got burn relays.

Please let me know of any questions.

Thank you.