I dont know if this helps. It seems you are doing Hairpinning (https://en.wikipedia.org/wiki/Hairpinning) The release notes for the latest firmware version have the following information: CSCvp01703 Description: RV34x: NAT hairpinning doesn't work when the InterVLAN Routing is disabled. Workaround: Create firewall access rule to permit the traffic to the particular LAN server. If this does not solve the problem you may be able to work aroud by using split DNS External DNS (used outside) will resolve to the external IP Address. Internal DNS (used only in the internal network) will resolve to the internal IP Address. Your internal clients will need to use the internal DNS.
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I had the same problem. I noticed that if I go to Administration - Reboot, the inactive image is on the older version as is normal. I think the router is detecting that. I updated the firmware again, but loading the firmware file from my computer (I downloaded first from cisco website). Go to File Management - Manual Upgrade - Select PC - Select the firmware image that you downloaded to your cumputer and click upgrade. After the router reboots if you go to Administration - Reboot, the inactive image is the same version and the router no longer warns about the existence of a new firmware. I hope this helps
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