Hi, if you do the test I suggested (connect to shore; turn on use/store switch and measure voltage on your coach batteries), and if you measure 13vdc to 13.8 vdc approx., it means that your converter is charging the coach batteries OK. If you have the RV Custom BCC black box.....it also means that that 50 amp re-settable breaker inside the BCC (that you are talking about) is OK......and it means the coach battery latching relay is also OK (at least they are allowing charging current from converter output through to the coach batteries OK for this test).
The other basic test is connect to shore; turn off use/store (or called coach disconnect switch if you have the RV Custom BCC); turn on some coach 12vdc lights......do they work OK? This is checking that the converter is working and connected to your DC distribution fuses (lights anyway). I would expect if the first test passes you would also probably pass the second OK, but you never know when folks have been making changes in electrical system connections.
This might still be the coach latching relay failing as other posters have suggested, but lets do some basic testing first and go from there. There are many excellent contributors on this forum, and I may not be be able to reply for a few days.....but I am sure someone will continue to help.
There is a lot of info on line and in this forum about the RV Custom BCC. Let's first make sure you have one before going down that rabbit hole.