Hi Mandy,
Just to clarify, when you use a custom attribute display, the fields that can be viewed through the popup are configured when you click on the green configure button, highlighted in purple below:
If you only have a link to Survey123 configured in this popup, that is all that will display in the popup view. Typically the custom attribute display also needs to include a view of various attributes, as in the raw HTML markup below:
<b><font size="4">Feature Attribution</font></b><br /><br />
Date: {DATE_OF_VISIT}<br />
Visit Method: {VISIT_METHOD}<br />
Visit Purpose: {VISIT_PURPOSE}<br />
Activity: {ACTIVITY_TYPE}<br />
Description: {DESCRIPTION}<br /><br />
<font size="4"><a href="arcgis-survey123://?itemID=90405555825f48a394f6462a8ffaa223&field:ParentGlobalId={GlobalID}">Impact Survey</a><br /><br /></font>
The fields that can be edited are set through the Configure Attributes button (highlighted in red in the first image). Whatever fields in this that have the edit box checked should appear when you click the edit button in Collector. If you are viewing the custom attribute display popup, you have to click the top right button, and click Edit to go into Edit mode. Editing must be enabled on the layer in question in order to see this option.
If you have related records, these appear below the custom attribute display popup (i.e. they are not affected by using the custom attribute display).
Mikie