You might be wondering, why you couldn't use your credits feature to send invites to your exhibitors. There is a small piece of information that you might have missed.
Well, before sending exhibitors invites, you need to add an exhibitor profile.
To do so, select the exhibitors under the content section on the left panel as shown in the below image:
Click on the "Exhibitor Profile" as highlighted in the image below:
You have to mention the exhibitor profile here which will be displayed on your event page. (Refer to the below image)
Only after adding your exhibitor profile, you will now be able to send invites to exhibitors.
To send invites to your exhibitors, you may refer to this article for help.