This is the correct result when the "registrations count" value for the registration option on the CRM Event Record is set to 1 and you include a guest.  If this value is set to 1 and you include a guest, this means that the person purchasing the registration is not the person attending, and thus the registrant is marked as "Will Not Attend."  

There are a couple methods that can be used to avoid this scenario:

1. If both the registrant and the guest will be attending, select a more appropriate registration option that includes a registrations count >1.  (i.e., select a "Couple" or "Group" registration option instead of a "Single" registration option)
2. Adjust the registrations count on this registration option so that it includes multiple participants per option.
3. Instead of adding a guest to a registration configured for only 1 ticket per option, you can create two separate registrants for that registration option.  (i.e., instead of selecting "Single" and adding a guest, you can just enter two "Single" tickets and apply one payment to both registrations)