Hello shevsterg,
Thank you for visiting Apple Support Communities. It sounds like you're having trouble using effects with Portrait Mode on your iPhone 8 Plus. I'd be happy to provide information about this.
Take a look at this article: Take Portrait mode photos with your iPhone camera. Be sure to follow the steps under "Take a photo in Portrait mode" when taking a photo.
If you're still having trouble with your effects saving, try restarting your iPhone: Restart your iPhone.
If you're using the correct steps and restarting did not resolve the issue, reply with whether or not you're able to use other effects with out issue.
Take care.