I have had sessions like that, coconut.
There are times I just have no words. There are times I don't see any good in talking about something or talking about anything.
When I began therapy I idealized T and therapy and when the reality of T and the reality of therapy didn't match my idealized version, that could cause a shutdown. At those times, therapy feels foreign and unfamiliar because of the mismatch between the idealizing and the reality. How can one feel safe in that kind of an environment? They can't, so we just had to wait for it to pass. She accepted my silence, tried sometimes to pull me out of it and sometimes that did work because it grounded me. Other times it didn't work and it made me mad, not that I would say so...

How to re-engage? The issue now in the forefront is the shutting down and all the things around that need to be talked about. You identify this as a way of not talking about something in particular so that's something to talk about. Maybe it isn't the right time for you to talk about it. Maybe there's something associated with talking about it that's troubling, such as being more known to your T. Maybe you feel it is more than you want to 'give' to T at this time. Maybe you don't feel like 'giving' anything to T right now. Maybe you feel like withholding something very important from T for punishment or to feel some control, power.

I think we talk when we are ready and we can be encouraged, but if the encouragement feels like pressure, we resist and that's a reasonable response to pressure whether that pressure comes from within or without.