Stimulus Check Question

I received my pre-check notice that a check was coming. It didn’t. I called, the Govt. couldn’t even put me on hold. (Call back later).
I went online and barely managed to get through to the “Where’s My Stimulus Payment” page. Got the message “There is a delay in processing your Stimulus Payment.”
That’s it. I can’t even get back to that page anymore. All I have is "Mention reference number 1647 to the IRS Customer Service Rep.
Anyone know what this reference number means? :confused: