Sorry about your issue, this could also be because you are using a non supported HTML markup, see this thread for two links about authorized tags (see the last for what's authorized in the title/subtitle. There is slightly different tags authorized if you are storing your images in Online through a Feature Services, if you are not using a Feature Service, the latest link will also apply for your points caption) https://community.esri.com/message/536215#comment-536215