If you can see the .cfg files, but they do not appear in the routers2 frontend, then this will usually indicate that the .cfg files are empty or have no valid targets.
This would in turn usually be caused by one of -
1) you have the wrong community string specified in the myrouters.txt
2) your monitoring host does not have rights to SNMP query the device
3) the device doesnt support SNMP at all
4) there is a firewall in the way
5) The device has unusual interfaces that cannot be uniquely identified by the ifName parameter
For (1), (2) and (4) you can correct your security settings. For (3) you will need to buy a better router or get a management module for it.
If the case is (5) then you will see a lot of Targets in the .cfg file, but all commented out with an explanation of why they are ignored. In this case, you might want to run cfgmaker to generate the files but with different parameters - eg, ifno instead of ifname, and so on. See the documentation on
http://www.mrtg.org to tell you how to manually configure a .cfg file.