DynamoDB Update item via Form

I'm trying to update an item in dynamodb records, the value of field I'm trying to update is from an input field in a form named joinedCSGroupAtDateInput. The resulted Expression Attribute Value is {":timeNow":"2021-02-16T05:21:55.887Z",":joinedCSGroupAtDate":"test"} which throws an error as once can see in the screenshots. If I give a static attribute value as above then it works. I'm confused, what's the issue her. Can anyone help?

Hi @pushkar_convosight!

After taking a closer look at this, it looks like this syntax is being evaluated differently from the static version:

Here is a syntax that managed to get a conditional update statement working for me:

Hopefully this helps!