GAPI Export to Google Sheet Invalid Argument Error

I’m trying to export details from out app into a google sheet and am getting an “Invalid argument” error. I’m trying to take the data from the page and also grab users’ birthdays on export. We use firestore as a db.

exportStaff(shift) {
      console.log(shift)
      const exportHeaders = [
        "Day",
        "Event",
        "Position",
        "Start",
        "End",
        "First Name",
        "Last Name",
        "Phone",
        "Email",
        "Confirmed",
        "DOB",
        "Code",
      ];
      const exportItems = [];
      for (var key in this.orderedPlacedUsers2(shift.id)) {

        function myDOB(staff) {
          return fb.usersCollection.doc(staff).get()
          .then(doc => {
            console.log(doc.data().dob)
            return doc.data().dob
          })
        }

        exportItems.push([
          shift.day,
          shift.event,
          shift.position.title,
          shift.startTime,
          shift.endTime,
          this.orderedPlacedUsers2(shift.id)[key].firstName,
          this.orderedPlacedUsers2(shift.id)[key].lastName,
          this.orderedPlacedUsers2(shift.id)[key].phone,
          this.orderedPlacedUsers2(shift.id)[key].email,
          this.orderedPlacedUsers2(shift.id)[key].confirmed,
          myDOB(this.orderedPlacedUsers2(shift.id)[key].userId),
          `=REGEXEXTRACT(H2,"....$")`
        ])
      }
     
      this.$gapi.getGapiClient().then(gapi => {
        const exportService = new ExportService(exportHeaders, Object.values(exportItems), gapi);
        exportService.export();
      });
    },

All of the birthdays are logging correctly to the console, but no values show on the sheet.

Here is a screenshot of the error in the console.

How can I get the birthdays (DOB) to export properly?