Issue with getting a string accepted and displayed as list media in Studio 3.

preview: {
    select: {
      title: 'title',
      type: 'campaignItem._type',
      start: 'startTime',
      end: 'endTime',
    },
    prepare({
      title,
      type,
      start,
      end,
    }: {
      title: string;
      type: string;
      start: string;
      end: string;
    }) {
      let status = 'Ingen dato';
      const now = new Date().toISOString();
      if (start < now && now < end) {
        status = 'Pågående';
      }
      if (now > end) {
        status = 'Utgått';
      }
      if (start > now) {
        status = `Begynner: ${start}`;
      }
      return {
        title,
        subtitle: (
          <span style={{ backgroundColor: 'red' }}>
            {status}
            {titleFromType[type]}
          </span>
        ),
      };
    },
  },