Charles_Gibbs:
the Victron connect app
I did not understand until now that you are trying to connect with some Victron software running on your PC. I thought you were trying to connect your Arduino to a Victron hardware device that sends data over a serial link.
Please explain what is the normal (Victron intended) usage of the Victron PC program and what you are trying to do that is different.
Do you have access to the programming interface for the Victron PC program - if not I suspect you are faced with a lot of long nights and a lot of coffee trying to figure it out.
Without the details of the programming interface it might actually be simpler just to write your own PC program to collect and display whatever data you want.
...R