Unusual Circumstance-E Filed Return

Here is a situation I encountered-thought the community may be interested.

I e-filed a 2018 1040 for a client with a refund due. The acknowlegement was received in a timely manner and I have all the documents that say the IRS accepted the filing.

This year, after e-filing the 2019 return, my client received an IRS notice informing him that they would not process his 2019 refund until his 2018 return was filed. This notice was sent from an east coast service center.  Client is located in Hawaii so normal service center is Fresno. The notice was replied to with all verifying documents included.

Then, a month or so later, he received a similar notice from the Austin Service Center...this was replied to in the same way including a letter of explanation that he had already received a like notice that had been responded to.

Several weeks later, a like notice from California service center.

To date we have received no response to our replies which were all mailed USPS RRR and Certified Mail.

I am at a loss as to what is happening. I have been an EA for over 20 years and have never encountered anything like this.

My only thought is to file forms to have the IRS search for his refunds for the two years in question. 

What do you think?