Channels
Verify that specified channels to be output are selected. By default, this is set to RGB, but may need to be set to RGBA is alpha is required in output.
File Path
Check if the file path has new, non-existing directories applied in path. If so, enable the Create Directories option.
Create Directories
By default, this is disabled, but should be enabled if the defined file path includes directories that do not exist.
Version Number
Include the version number notation as 'v01'. This allows for using the ALT + Up/Down keys to iterate through version numbers when selecting the Write node. Verify that a separator is placed before and after it. For instance:
_v01.###.exr