Thank you for posting in the Community, @geofabinds.
I've got some insights to share why the GSTR1 and HSN reports are not matching.
HSN is for inventory items. Ideally, you'll need to create a service item instead of inventory since you're using a code for services. Here's how you can do it:
From the left pane, open the Sales tab.
Click on Products and Services.
Fin the items of the type Inventory and Non-Inventory for which the HSN/SAC column is blank.
Select Edit from the Action column, edit the HSN code, and hit Save.
For future reference, you can also review these helpful guides to resolve possible issues on reports: