YongSang, (strangely, it’s tricky to find the English Manual for your ASUS RT-AX82U Router! Nevertheless)…
Assuming your router doesn’t have any other configuration problems, the one main configuration that could cause problems of connectivity between Mosaic and your Network Bridge has to do with IGMP Snooping. Make sure the “Enable IGMP Snooping” configuration is Disabled**
You’ll find it within your Router’s config page as shown below;
If that’s already disabled by default, and you still have a problem, then step 1 to solving it is to ensure your Network Bridge has a proper IP address allocated to it (you can check from your Router’s “Network Map” page”) and verify that you can connect to the Network Bridge from any PC/Mac Browser.