Phone rings but you can't hear the caller

This is almost undoubtably a network issue of some sort.

Does it happen just for one user or many?  
Desktop phone on computer or hard phone or both?
Has it always happened or started recently?

Do you have any knowledge of your internal network setup?

Happens for many users on all of our desktop phones.  This started a couple weeks ago.  Not sure of our network set up but I can find out if you tell me what to ask.

Can the caller hear you? If so, youre describing one-way audio. The most common reason for this occurrence is having SIP ALG activated/turned on in your router configuration. SIP ALG is also known as SIP Forwarding. SIP ALG can change/modify and mess with voice (read VoIP) packets. It should be turned off or deactivated. As stated, this is only one reason (although usually the main one). If yours is turned off and you are still experiencing this issue I recommend starting a ticket with RingCentral support.

Not sure if they can hear me or not.  I'll have IT check.

IT here. Is this guide still accurate for configuring rules on a Meraki MX64?
https://netstorage.ringcentral.com/guides/meraki_mx64.pdf

Is this still an issue with anyone? We receive these calls all day long where nobody is on the other line. We will sometimes wait several minutes to see if the call is being transferred to a call center or something, just to see if it's even a telemarketing call. However nobody ever comes to the line. We've even called several numbers back to find they are not legit numbers.

A while ago we had settings that were not correct and when we couldn't hear anyone on the other line, we would hang up and they would immediately call back. None of these callers call us back so we think it's not a setting. 

They all have caller ID, most of the times it's a city/state with a phone number but oftentimes there is a name and a number. 

I know of the tactic to determine if a number is legit in order to then give the number to telemarketers, but we don't end up getting many telemarketers, so it doesn't make sense.

We are going to try adding a layer where the caller has to press 1 to reach someone. Currently, the calls ring the whole office simultaneously without any layers in between.