If you see the SSID HotSpotSystem.com-…., then the installation was successful, so probably it is a DNS problem and you need to set the DNS manually. Your DNS settings is depending on your ISP, and your local ISP should supply you the IP address of their DNS.
For DNS servers you can use Google’s public DNS:
18.104.22.168 or 22.214.171.124
as your DNS servers.
In DD-WRT this can be set up under Setup > Basic Setup > Local DNS.
Then restart your browser and also your computer, then try to connect to the router again. If you get an IP from the range 192.168.182.xx (usually, but this depends on the firmware you are using) then it is good. Try to browse the internet, you should be redirected to your hotspot Start Page.
IF YOU STILL DON’T GET AN IP FROM THE ROUTER…
This can be a wireless channel issue. Try to set the router to a different channel in DD-WRT, on the Wireless page.