From other discussion from yesterday (helped for me):
Hi All,
The following steps fixed the issue for few users. Please try:
1. Uninstall all 12.x version of Premiere Pro.
2. Backup the Preferences before next step(~/Documents/Adobe/Premiere Pro/12.0/Profile-USER)
3. Rename the following list of folders to Old_foldername.
~/Documents/Adobe/Premiere Pro/12.0
~/Library/Caches/Adobe/Premiere Pro/12.0
~/Library/Preference/com.Adobe.PremierePro.CC12.plist
~/Library/Saved Application State/com.Adobe.PremierePro.CC12.savedState
Note: All the above folders will be in the hidden library. Here are the steps to access it: Access hidden Mac OS library files
4. Empty trash
5. Reboot the machine.
6. Install the latest version(12.1)
Let us know the status.
Thanks,
Vidya