Solution
This error is usually related with an incompatibility between the Vision Development Module and the TensorFlow versions used to create the model.
In order to use the IMAQ Deep Learning network models, you will need to compile the .pb model file to the lowest TensorFlow version compatible with your Vision Development Module.
You can check which TensorFlow version you should be using by reading the LabVIEW Detailed help for the IMAQ DL Model Create function you have installed, as seen in the image below for Vision Development Module 2019.