Hi Tom,
Did you try deleting the survey within the app and downloading it again, not just doing an update over the top of the survey. If that doesn't work you try uninstalling the app, installing again, then downloading the survey?
Alternatively, it could be the way you created the csv. Is the look-up csv table you mention an external choice list? Did you create it originally as part of the xlsx file as an additional sheet (external_choices), which in turn created the csv file in the media folder. If so, you need to edit the data in the external_choices sheet and re-publish, which in turn will update the csv file in the media folder.
If you are editing a csv file that exists in media folder only (not external_choices list), used by pulldata() for example, you should just be able to update the csv in the media folder and republish as you have done.
Another way to update a csv file in the media folder of the Form item in AGOL or Portal, without the need to republish the survey, is using python and the following method: https://community.esri.com/groups/survey123/blog/2017/12/08/an-alternative-way-to-update-the-media-f...
Regards,
Phil.