I had the same kind of issue when I upgraded our app from 9.18.4 to 9.24.1
I was able to resolve it by updating the libraries.
Here is the list of libraries used by default in mendix 9.24.1:
I created a new project in mendix9.24.1, copy pasted those libraries in my real project , and removed old (duplicated) ones.
Hope that helps.
Updating the SAML module to the latest version is what worked for me.