I run into this in periods due to working too much and just not having the energy. The key for me is to give up on any intellectual ambitions for a while, and just go for something that’s quick and easy to read.
After I’ve started reading regularly again, I can then ramp up the difficulty until I suddenly reach that stage again where I feel like “it’s weird how I just don’t read anymore”, and I have to start over.
At my age, this has happened more times than I care to admit. With some people, it’s like no time passed at all, and everything is great.
With others, it has become very evident why we lost touch.
I haven’t discovered a way of seeing who is what type without just trying to reconnect and seeing what happens.