The hosts on each of the ethernet networks need to have the e0 interface IP address of the router on their LAN, configured as the default-gateway. Then a host on one LAN can PING a host on the other.
If the problem is not quite what I am understanding from your question, then please post the configurations here and I can take a more detailed look.
Run a tracert (Windows) between hosts on both sides of the routers. Provide those results for further analysis/discussion. Tracert will show how far ICMP (ping) packets go before being dropped. This will tell you if the data is crossing the link(s) but not making it back to the sender. I have seen traffic go across a link but not return due to a misconfiguration on the receiving side. It may look like a sending side error – that is why you need to check the traffic going in both directions.
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