Aqualung ppa works on Laptop but not Desktop

[oldrocker99]

After ten years of using Ubuntu, on my 16.04 Ubuntu MATE laptop, the PPA for Aqualung works just fine. I've never seen this before, and it did work on previous 16.04 installations. (I tried 18.04 beta, and had problems with it, so I reinstalled 16.04.)

On my 16.04 desktop, I get a recurring 404 error.

What the fred is going on here?

[mc4man]

Maybe you have a bad address on the desktop, remove the ppa, update sources, add back ppa, update sources, see.