Recently, my SONAR's projects have been changing 24bit to 16bit.
I created a new project with 48kHz 24bit, and the transport displayed " 48 24 ".
But, I close and open the project several times, and I suddenly realize that transport is displaying " 48 16 ".
I don't know the cause is SONAR or Audio Interface  (UR242) or some other software, but I want to know how can I restore the project 16bit to 24bit.
Of course the recorded audio files are formerly 24bit, and now 16bit.
sorry for my poor English.

The bit depth in the transport is the "Record Bit Depth" setting in Preferences > File > Audio Data

I'm not 100% sure, but perhaps there's an early backup from the original save, that might be restored at the original settings. 😊 Someone more knowledgeable than I may confirm/deny. I've done similar but I made copies of my original on two drives. Then I work with one, leave the other alone in case I need it.

I failed to mention SONAR can work with clips at different bit depths. The setting in the transport reflects the bit depth of any future recordings. The bit depth of any previously recorded material was made at the "Record Bit Depth" at the time of recording. SONAR does not change bit depth of existing clips when the "Record Bit Depth" setting is changed.
 
One more thing, the "Record Bit Depth" has nothing to do with the Preferences > Audio > Driver Settings "Audio Driver Bit Depth" value.

Thank you for your advice. I checked the Preferences>files>Audio data, and change the Bit Depth Value.
I think I didn't change this parameter. I don't know why the value has changed.