Users not Receiving Emails or SMS

Randomly some users are not receiving SMS or email notifications.  It has happened to a few employees now without any rhyme or reason.  The employees email/sms are working correctly for everything else.  Our email filter is not blocking anything and the provider is stating they are not seeing the emails hit the server.  The other strange thing is that when I change the email address on their RingCentral account to my test email address the emails still do not come through but when I change my RingCentral account to my test email address they do come through.  The other strange thing is that it “normally” corrects itself the following day without any intervention.

I had previously opened a ticket with support but they keep insisting it is something on our end.

Has anyone else experienced this?

Thank you