If you are on a Korean system or you set the language to Korean, DanceXR will not load properly in 1.4.7 and 1.4.8. We are very sorry for the trouble and will address this in the 1.4.9 update.
For now, there is a simple workaround that you can use to get DanceXR working again, if you are OK with the English version.
Right click on DanceXR from your Steam library, select Manage / Browse Local Files
Then open "DanceXR HD Pro_win64" folder and open config.json file with a text editor
Scroll to the bottom and you'll see "language", change its value from 0 to 1
And then you should be able to use DanceXR in English.
If you need the Korean version, you can also revert back to 1.4.6 version by going into Properties settings of DanceXR in your Steam library. Then select the Beta tab and choose "1.4.6" from the dropdown.
We are really sorry for the trouble.