Value error in an embedding layer
It looks like you're using Keras, so this answer is going to refer to the Keras embedding layer.

The error message is pretty clear - Keras embedding layers don't accept strings as inputs. The embedding layer requires an array of positive integers and can only be used as the first layer of a model. The embedding layer requires that you encode each word as an integer so you might have to use the Keras tokenizer.

Source: Embedding Layers