RingCentral not receiving wireless calls

RingCentral is responsible for working out issues with other carriers for their customers.  Contact RingCentral and let them know of the situation and let them know that you expect that they will work with whoever they need to in order to fix it.

I have tried that route and they are claiming it is an AT&T issue. 

It may well be an AT&T issue, but you're not an AT&T customer, you're a RingCentral customer, and RingCentral needs to work with any carrier that's not bringing calls to them like they should.  If they insist that they will not work the problem, file an FCC complaint against RingCentral.

Speaking of the FCC, this is the response I received... "RingCentral can't contact the carrier and have it fixed because of **Federal Communications Commission (FCC) regulations**. These regulations exist to protect the originating caller's **Customer Network Proprietary Information (CNPI)**."

Well, if RingCentral can't get AT&T to fix it (for whatever reason), I guess you'll have to switch providers to someone who will work with the other telephone companies when a routing issue occurs.  Because that's what telephone companies do.  If the above is their response to the FCC complaint you already filed, then you should tell the FCC that you don't accept that resolution because it's horse manure.

You can try the AT&T Business Forums at https://bizcommunity.att.com/ for additional suggestions.

Wait... one final suggestion:   Did you port your phone number from AT&T to Ring Central??  If so, open a porting complaint with the FCC saying your port didn't complete.

No we have been on RingCentral for 4 years and this didn't start happening until a few months ago.