Our router, admittedly an old D-Link in a home office environment, firmware updated 3-4 yrs ago, suddenly refuses to connect to our tax prep software service. I have to disconnect from the router and connect directly through the cable modem. Over the years that we have used this router and this configuration this is the only website that causes me problems.
This persists with all computers on this router.
We have reset to factory settings. That doesn't work and it takes a good days work to get it reconfigured again. We're not techies here so it takes us a bit longer to do that while still trying to get some work done.
Suggestions for other places to look; registry, lookup tables, etc?