This paper seems to be re-treading the same path as the Novikov self-consistency principle. The conclusion is the same in either case: Time travel is not possible when it creates paradoxes. It says nothing about possibility, only about impossibility.

For all that we know, all attempts at time travel may be impossible, since they may always lead to paradoxes. In this case, even if you could build a time machine, it would automatically shut down every time you tried to use it.