"Fetch entity by property" for users that share terms with new node
I think the reason for this is that the 'Value' property is asking what you want to match in what you are looking for, basically in pseudo terms, what you've got above is:


Find the Entities of type: User
Where the Entity's property: RFP Category
Is equal to: The author of the node's Categories


This is where your selection falls down, because you're trying to search for a set of answers where the data matches an Array. If the node you create can only have 1 term entry (not multiple), I would use the action 'Add a Variable' and set it to the taxonomy term you've created on your node, something like

Add a Variable > Taxonomy Term > [node:RFP-Category] I'm guessing to your setup

This will create a new token for you which contains the Taxonomy term you're searching for. Then in your Entity query, you can use this as your value property

eg 


Find the Entities of type: User
Where the Entity's property: RFP Category
Is equal to: [Your New Token]


If your RFP category has more than 1 or unlimited values, you will have to create a loop of the categories on the node first, then use 'Add a variable' and carry on with the same method