Make sure that the users that can't see the HubSpot fields in Gong have read access to those fields in HubSpot. On the HubSpot side, access is given by your HubSpot admin.
Why is my call not visible in HubSpot?
If your call is not appearing in HubSpot, it could be that your HubSpot contact is associated directly with the deal, and not with an account. In order to connect calls with deals, Gong finds the contacts and their accounts and then attaches the call to the relevant deal.
Why is a datetime HubSpot field not displaying correctly in Gong?
If the field you are importing is a datetime field and is set up as an equation, you may need to check the format the value is saved in and whether it needs to be converted to display correctly in Gong. For more details, see the HubSpot documentation.