|A link to this guide you're using might be helpful.|
" Problem occurs in next frame called 'Network Setup' it is requiring a 'router IP' & subnet mask again and will not accept either the 1st or 2nd router IP address -"
sounds to me like it's possible you're being asked to configure the LAN IP address on the second router.
If you've connected from a LAN port on router 1 to the WAN (internet) port on router 2, this is likely the case.
Question: Are you setting up the second router to have a second, separate subnet from router 1? If not, and you're just trying to extend the LAN configured on router 1 then you should be interconnecting the two from LAN port to LAN port
Click on my name above in this response and read my “how-to” guide titled, “Add a second Router to your LAN”
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.