When dealers cannot connect to their Main Repeaters through a router, but can connect directly to the repeater, it sometimes indicates the router is blocking the communication in some way. The most common reason for communication being blocked is that the multicasting ability in the router is blocked or disabled.
Some routers have multicasting disabled by default. some don't. We would recommend logging in to the router and enabling multicast then try to save settings on the "find main repeater" screen. Sometimes, the settings for multicast will not explicitly call out it is a multicasting feature. The most common nomenclature we have seen is "IGMP Services". Enable the IGMP Services to enable multicast.
If you cannot identify where the multicast setting is on a router and are unsure if the router has multicasting enabled or disabled (and a google search is not fruitful), we would recommend contacting the router manufacturer for assistance confirming this matter.