Download the latest 5.7.1 directly from here and install this.
There's no need to install 5.0 first.
Does your code start with 1160 and is consisting of numbers only - Do NOT post it here?
Is it an upgrade code? If yes, you'll also need the code for an older version.
Exactly what do you mean by not accepted. What error message?
If it is an upgrade serial number you also need a serial number from a previous version.
It also needs to be a serial number from the version you are installing. If you have a full version LR 5 serial number you need to install LR 5. Not LR 4 or 6