@jscheeracnp @jessicasch Your expression looks like it's missing the dynamic content.
Try creating the expression in this way. Add a Compose action and insert an expression. Use the empty() function.

Click on the Dynamic Content tab and insert the dynamic content from the Get Response details action of the date question.

Place your cursor at the start of the expression by pressing the UP arrow key. Enter if and an opening parenthesis.

Go to the end of the expression by pressing the down arrow key. Add a comma and the word null and another comma.

Insert the dynamic content from the date question again.

Add a closing parenthesis.

Run a test. If the date question is empty, the Compose action will return null, if it's not empty, it'll return the selected date.
You can now use the output of this Compose action in your Update Item action.
You might find these two YT Tutorials helpful:
How to Get Microsoft Form File Uploads Attached to an Email 📧
In this section I cover how to create a dynamic content key that will output an email address/addresses based on a selection from the form. You can use the same logic in your flow.
I also cover the following in the tutorial above:
✅ Two types of MS Forms
✅ Where Microsoft Personal (OneDrive) Form File Uploads are Saved
✅ Where Microsoft Group Form File Uploads are Saved
✅ How to Add a File Upload Question to an MS Form
✅ How to get a Microsoft Form ID
✅ How to get a Microsoft Form Response
✅ How to Get the Dynamic Content Microsoft Form File Upload Content
✅ How to handle Single and Multiple Microsoft Form File Uploads
✅ How to use a Scope action to Organize and Group Your Flow Actions
✅ How to Get the File Content from an MS Form File Upload
✅ How to Collect All Files Uploaded to a MS Form and Attach to an Email
✅ How to Handle MS Form Response When a File Isn’t Uploaded
✅ How to Create an Email Key
✅ How to Send an Email to a Specific Recipient Based on Form Selection
✅ How to Create a Dynamic Output Based on Form Selection
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You might also find this YT Tutorial helpful: 5 Power Automate Troubleshooting FAQs and Helpful Tips for Creating Better Flows
IN THIS VIDEO:
✅ How to troubleshoot a false Condition action result
✅ How to get dynamic content when it isn’t selectable from the list of dynamic content
✅ How to troubleshoot an Apply to Each action that isn’t looping through
✅ How to troubleshoot a skipped Apply to Each action
✅ How to troubleshoot a Filter Query
✅ How to use a SharePoint yes/no column in a Filter Query
✅ How to use Compose actions to troubleshoot a Power Automate flow
✅ How to troubleshoot multiple emails being sent
✅ How to troubleshoot multiple Teams messages being sent
Hope this helps!