Congestion - only on one ata box, and only from incoming calls via a DID,not interna calls

I recently have learned that one of th epoeple on my FreepBX set up that has their own DID, have issues with incoming calls made via a DID.

If someone calls, the call gets answered, and forwarded to the extension. But, the extension never gets the call, but yet the person calling hears it “ringing”.

The CDR files says call “Failed” and the App says it used was “Congestion”.

The extensions can be called directly, and works fine.

The person can also make outgoing calls with no issues.

I thought maybe it was an issue with teh DID transferring. So, I used an incoming call from a separate DID and tried transferring to the same extension that waserroring, it was fine.

I have two phone line connections on the ATA box and it gets the same error.

I amwodnerign if someone might have an idea to the cause of this?