Waveshare RS485-CAN-HAT (MCP2515)

[Techstyle]

I have added a Waveshare RS485-CAN-HAT to my Pi 4 with OP2 installed.  I enabled SPI and hit the 'Add MCP2515 device' button.  I pressed the 'Add connection' button:
   
In the Signal K web interface the can0 says 'connected' and the can0 connection appears to be configured right:
   
interestingly, if I change from 'Canbus (Canboatjs)' to 'Canbus (Canboat)' can0 says 'Started' - not sure if this is of interest?

I have the H and L connected to the seatalk NG can High and Can Low from a NG backbone with two terminators and a Raymarine Axiom MFD as an input and I don't see any sources on the MFD or incoming messages on the data browser in Signal K

I have the Signal K to Nmea2000 configured to output just COG and SOG to limit traffic for now but still do not see any source in the MFD or anything incoming to signal K

Does anybody have any ideas what is wrong?

I did notice that on this page that the recommendation for this device is:

Code:

dtoverlay=mcp2515-can0,oscillator=12000000,interrupt=25,spimaxfrequency=2000000

but I have 

Code:

dtoverlay=mcp2515-can0,oscillator=12000000,interrupt=25

not sure if this is the source of an issue, but it doesn't fix it