All the above are excluded, I already explained.

How about a temporary vulnerability in the Electrum 4.02 version? What do you think about that?

Yes, that is correct.
I have just checked my OS for viruses, fake apps etc. Nothing shows up

I  have also tried generating a new address now on the 4.02 version NOW, I have checked it and it is valid, it is belonging to my wallet.

I did verify it, I'm using electrum and dealing with BTC for many years now. I know what I'm doing.
I have used version 4.02 for weeks now, received multiple payments with no problems. I have today upgraded to 4.05 thinking maybe the payment is not showing because of this.
I also received 7 payment yesterday on another wallet, so if someone hacked me in any way, he would have gotten multiple transaction from me.

I am not using a fake version of electrum. I have used version 4.04 for weeks now, I got multiple other payments with no problems with the same wallet. I have today updated to 4.05

I forgot to mention that the transaction do show on blockchain, so the customer did send the funds

Hi, on November 25 I generated a new bitcoin address with my Electrum wallet and loaded it in my website. Yesterday a customer contacted me to say that he sent a payment of $1800 and that he didn't receive any confirmation.
I checked my electrum wallet and there is no money in it. I am 100% sure I used the right address, and copy-pasted it correctly, I have done this thousands of times.
More than that, when I try to generate a new address and also look into history, it looks like I never has that bitcoin address, like it's part of another wallet.
Is this because of the DDOS attack? I'm panicking because of this, this is a very big deal for me. Please let me know if you know anything.
I'm using the latest version of electrum, I also restarted the program and also my PC.
Thank you!

Yes, I have bought a couple of miners from them, they're pretty much ok.