Thanks for the samples.
Only the XMP metadata differs between the two DNG files you provided me. The previews are the same in both files. Because the second DNG's preview does not reflect the changes you made to the Adobe Camera RAW settings, the preview shown in PM also does not reflect the changes you made in Adobe Camera RAW.
You need to find some way to force the preview to be updated of PM won't show you what you expect to see.
this is the preview in PM: https://drive.google.com/open?id=0B4Fs7P7gqlcJMTFlY25wZzAtUjA
this is the preview in Adobe Bridge: https://drive.google.com/open?id=0B4Fs7P7gqlcJLVdPZXlaeGY5TWM
and the DNG file is the same. Why? Please, help me.
Bridge is rendering the DNG file. Photo Mechanic cannot render the DNG file because Adobe doesn't give us their rendering technology. Photo Mechanic must display the embedded JPEG preview of the DNG file. Since your DNG file's preview does not reflect the changes you made, PM doesn't show them.
You need to find some way to get Adobe's tools to update the embedded preview in your DNG file. Earlier, Hayo Baan told you how to accomplish this:
Are you definitely making changes to the files in Adobe Camera Raw and are you closing the dialog with DONE and not by quitting the dialog with e.g., ESC? If so you should see a (brief) dialog window where Photoshop shows you the progress of the save and DNG preview updating.
Please make sure you're properly updating your DNG files.
If the preview isn't updated then you won't see your adjustments in PM.
-Kirk