Is. there a limit to the number of VNT CAN Transmit and CAN Receive blocks that can be used in a model

I have created a Simulink model which performs communications with a number of CAN devices that are included in our system. The CAN blocks are configured to use a KVaser Leaf Ligtht USB CAN tranceiver. This model used to work with VNT communications to all of these devices, but as I have added communications for more CAN nodes into the model, it has stopped working. I get an error message:

Could not open CAN device to connect to the network.

If I comment out one CAN node, this message goes away and the simulation runs again.

Is there a limit to the total number of VNT CAN Transmit and VNT CAN Receive blocks that can be used in a model?

If there is a limit, does anyone know a way around the limit. This is becoming a problem for my development.