Two things.

1. d65cafc-1435-45d3-acce-dc464f02c4b1 is not a proper UNIQUEIDENTIFIER. The first grouping only has 7 characters when there should be 8.

2. Don't rely on implict conversions. CAST the GUID string to a UNIQUEIDENTIFIER and compare it to your column. Don't CAST the column to a string as SQL cannot seek on the index (assuming there is one).