Can you send an example of some of your training data showing how the synonyms are defined and then a log with --debug so we can see what’s happening during a dialog where you test out the synonyms?
In other case ,i have trained Shipped with shipped, carried, Dispatched synonyms.If i use some synonyms for Shipped other than trained synonyms ,rasa is not extracting the entity as well.
Make sure you have NLU training examples with the synonyms:
what are the [shipped]{"entity": "delivery_status", "value": "Shipped"} order counts
how many [carried]{"entity": "delivery_status", "value": "Shipped"} orders are there
number of [Dispatched]{"entity": "delivery_status", "value": "Shipped"} orders