Don't hear any sound in any of our Asterisks. What should i do to fix that?

Anything that can help me out with that? I have many customers calling and trying to get a hold of me and I have to use my cellphone to reach them. That is very inefficient because there is only one of me and many customers. It is also very hard to reach all of the customers in one day because it depends on what their calling about and how long the call is.

Not sure what your problem is. Can you be more specific about the issue you face?
I see you have mentioned the audio issue in your subject but there is not much information apart from that.

I can imagine two scenarios.

1 - Asterisk servers on cloud

2 - Asterisk servers on another Vlan that was reached by your network gateway

For both scenarios, you or someone else, made changes at network structure applying changes to routes, NAT, firewall rules and related.

That are the main reason once you said about all your Asterisks presenting the same failure.