Creating graphs of CNN models: cannot use plot_model from keras.utils.vis_utils
I had exactly the same problem today and stumbled upon your question. As it had no replies, I dug further and eventually found something that helped me. For you it may be too late but anyone else having this problem, maybe it helps if I document my finding.
For the background: my setup is Python 3.7 under Windows 10.
The keras function plot_model uses pydot which itself relies on GraphViz. Moreover, the error message Format: &quot;ps&quot; not recognized. Use one of: you see is caused by dot, one of the tools that belongs to GraphViz, which is called from inside pydot. After playing around with the dot tool, it eventually told me the following:
There is no layout engine support for &quot;dot&quot; Perhaps &quot;dot -c&quot; needs to be run (with installer's privileges) to register the plugins?
So, I fired up a new console with administrator priviliges and ran dot -c. This enabled dot to use its layout engines and this made the error disappear. After this,  plot_model suddenly worked for me.
Hope it helps anyone.