CAN loopback not working unless bus monitor online?

[JoshDiJoseph]

Hi,

I have a strange CAN issue 

I have a VI which reads and writes signals referencing an XNET alias for a dbc file.  This VI has been used over and over with no issue running on LV 2018 SP1 and XNET 18.0 with a NI USB-8502 CAN adapter.  We moved the VI to a new computer along with the same USB adapter, now running LV 2024 Q3 and XNET 2024 Q3.  Strangely, the read portion of the VI works right off the bat, however, the write does not show up on the CAN bus (monitoring with CAN King/Kvaser USBcan Pro as well as the inverter I am trying to talk to). 

However, the strange part, if I open the CAN bus monitor in MAX and run it, the signals immediately show up on the bus/inverter.  No MAX bus monitor, no go.  I can not for the life of me make sense of this.  Any thoughts?

FWIW this behavior also occurs with a PXI-8512 CAN card in a PXI-1088 on the same computer (running 64bit windows 10).

[billybaru13]

Some additional details:

- when I write to the CAN bus using the attached VI with the bus monitor off I get an error frame instead of the intended message

- when I write to the CAN bus using the attached VI with the bus monitor on I get no error frame and the correct message is observed on the bus

I'm pretty green as far as CAN goes.  It's quite possible there's an obvious solution but it very much seems linked to the version of LV, XNET or Windows (permissions/firewall or something along those lines).

[JoshDiJoseph]

Sorry about the  account confusion - was using a machine that was logged in as another member without realizing.