Get an Ethernet patch cable long enough to reach the camera's RJ-45, run cable from cam to router LAN port and on your PC pull up the cam's web GUI by typing in its IP address using Internet Explorer, if you know it.
If you don't know the cam's IP address, run the
Amcrest IPConfig Tool to find it.
Once logged in, do what you did before on your old router to locate your wireless and set the camera to it (under 'setup', 'network', 'wi-fi'; then find your wireless SSID, connect, save).
While in there, change IP of cam to static if not already static and write it down somewhere if you had to use the IPConfig program above to find it.
Wait 2 minutes after it finds wi-fi and says it's connected before you pull the Ethernet cable.
Wait another minute and
ONLY if not working, pull power to cam for 15 seconds then re-apply power. It should be on your wi-fi in less than a minute.
You can also do this with a laptop and short Ethernet cable close to the cam but that involves making temp changes to laptop's IP addressing schema, etc. and if the above works for you then no point in getting into all that.
Hope this helps!