So I want to request an ETH payment from a site were I have put the wallet address a month ago.
Today when I request the ETH address again to compare if is everything is ok I notice that today's address is different than the other I got a month ago!
Is this normal? Can I request the payment or I have to edit the address?
This is done for security, re-using address is slightly dangerous. Though you can still re-use your old address. Once the address is generated, it's yours to use permanently.