Please add a bit more info to the question phonebook name, source type, etc..
From you error message it looks like TMS wasn't even able to resolve the Phonebook name (""). That space just has double-quotes. For a test create a new phonebook with a different name and use the same source and see if that syncs.
I have added 2 Video Endpoints on TMS for new location. First I have created new folder on TMS under which I have added these new VC. After completion of this I have created source under Manage Phone Book Source , where i can see the VC list in contacts but when I am trying connect the source with Phone book (Under Manage Phone Book) then it is showing error.
I have attached the screenshot of error in previous message.
Note : All formatting is correct since we are using similar pattern in our environment. I have also tried making new source but no luck