Hi Thijs Onderwater,
Based on microflow I see that you have not used pre-processing action which should be a java Action which converts your input into ml model input.
Based on Ml model the input is embedding_1_input which is a array of 1*20 size But in mendix we can only pass it as string(Embedding_1_input). so, we need to use a java action which can convert your input in a format of array and change this array as string and make the java action return the object Ml_input_Entity which is this converted string.
Hope this helps, if you need further assistance feel free to reply.