Hey Marc! 
It sounds like you’re passing text to the tags column and expecting it to convert the text to a valid hashtag. However, this isn’t how our tags column works currently. You’ll need to pass a numerical tag ID to the column in order to have #Aaron appear as a tag.
How about changing the column type to a text or person column instead?
You can use Integromat to look up a tag’s ID based on its text field, but it will be complicated based on our API’s current capabilities. You would need to get all the tags in your account and then look for the one whose name corresponds to the account manager. What do you think?