Q: shortcut of OF 2 for Mac clipping cannot be saved

I have OmniFocus for Mac 2.2 on OS X 10.10.3. I opened the Keyboard section in System Preferences. Under Shortcuts->Services->Text, I found “OmniFocus 2: Send to Inbox”. I added a shortcut, such as Shift-Command-, and exited the System Preferences. Then I went to the Shortcuts tab again, and found that the shortcut for “OmniFocus 2: Send to Inbox” was empty. I have tried the same thing for a several other key combinations but none of them was saved.
Do anyone else have the same problem? How to solve this problem?

If you’re still having trouble could you shoot our Support team an email? We’d be happy to look into this further with you! omnifocus@omnigroup.com