Merge to HDR Pro fails on large images with no error reported. it appears to work up until the preview exposure is set. A good preview of the final output is shown. After completing the merge the output is just solid black.
A ~21,000 x 5000 pixel image with 4 images in the stack failed. When I reduced the size to 25% it worked.
See this thread for discussion and link to sample images:
https://forums.adobe.com/message/7203...