"Unable to reach web admin..." means your computer is not connected to the router reliably. This error occurs when the router is restarting after a reconfiguration (usually, that is).
Can you connect your computer to a wired Ethernet port on the router and see if you can get to the administration Web page that way? You're not using the wireless radio(s) on the router, so you should have a more reliable connection.
Whatever problem you may have on the WAN side of the router, you need a reliable connection to the router itself.
What model PepWave router is it? I have a PepWave Surf SOHO, version 3. It appears as if the router management interface is similar to yours.
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