Date format issue while importing contact using Import Contacts automation in Qualtrics

I am trying to upload a simple CSV file into Qualtrics to import contact, within which I have a field called Transaction Data. When I am running the file into the automation, the Run status appears as Automatically retired and schedules a new run after an hour. When I looked into the details of the retired run, it said the following:
Errors
The Transaction Date column in rows 2 (where row 1 is the header row) had unsupported date formats.
Resolutions1Ensure that the Transaction date value is in a valid date format.
Valid date formats include RFC3339/ISO-8601, UnixDate, RFC822, RFC850, and RFC1123.


I am using a simple yyyy/MM/dd format in my CSV. I am not sure about the above formats.

Some help here will be much appreciated :-)