First is that Member Splash automatically creates a product called Front Desk Guest credit to track guest pass sales done onsite vs. those done online in advance. That product had been deleted -- the setting still is there in the database but the product wasn't. I re-added it.
The second issue is that the product Single Guest Credits didn't have the field for how many credits to award filled out. That's why credits weren't added to the accounts you mentioned. I set it to 1 so that future orders will automatically update the account.