.DNG files not accepted in "plug-in extras" invocation mode of TPAI 1.2.0

I used the lightroom photo merge to create an HDR image, resulting in a .dng file format. When opening the file in TPAI ver. 1.2.0 as a LR plugin using the “edit in” menu, it advised me to use the “file>plugin extras>process with Topaz Photo AI” approach to achieve better results. However, when trying that approach, the program tells me it cannot open the file because the image is not supported. This happened when I tried using a copy and also when using the existing file. It seems that TPAI recognizes the file as a raw format in one approach but then refuses to accept it when using the recommended way to open a raw file.
Any ideas?

Please see the thread on how to raise a bug report, and raise in the Topaz Photo AI, report a bug section. Please note also that Lightroom HDR DNG images are in floating point format and are not supported at this time. Try exporting a TIFF instead.