Appraiser "Unable to Complete Report"?

[Christine Smith]

Hello, we are in the middle of a refinance on a property in California. Everything is moving along and we had an appraisal last week. Appraiser came out, took photos, did a thorough walk thru on the property. Today I found out the "appraiser couldn't complete report" and we have to start the appraisal process over with a new appraiser. 

I'm left scratching my head and frustrated.

Why would this happen?