I'm starting to learn how to publish web tools from Pro to our portal and have made a simple ModelBuilder tool.

Tool works just like it should in Pro. However, after I publish it to our portal it always fails and I get the following error;

Not very descriptive and after searching for about half a day on Google it seems no one has the answer to this.
I'm running Pro 2.3.3 publishing to Portal for ArcGIS 10.6.1