I got chance to use the Physical risk and resilience tool (Sandbox UI) and found that under Asset module whenever a user loads the data using load portfolio feature, a blank row gets created in UI indicating the number of records.
Please view the below screen shots

As a result , I am not able to use the calculate impact feature as tool does not return any data
Requesting you to please look into the issue.
Looking forward to hear from you
Regards,
Vishesh Mangal