With the new updates, the file extension has also been updated. For some software, GeoStru has created a specific converter, as in the case of Slope and SPW. For most other software, you can open files with the old extension by simply changing the file extension filter in the Open window. If the old extension does not appear, the software may not be able to open files from older versions.
For Downhole, you need to rename the file extension from. dwh to .dwhx (in this case, you need to display file extensions in the system settings: in Windows 11, simply open any folder, go to View > Show > File name extensions).