Clematis wilting

Hi,

I have a clematis Montana that was doing great until recently and suddenly its leaves went really droopy (the whole plant).

I tried watering it more but this didn't help. I have read that Montanas are quite resistant to clematis wilt so I guess that wouldn't be the most likely scenario (?). The only other thing I can think of is over watering.

Any ideas? I am not keeping my hopes up for this plant recovering but it would be really good to know if I can replace it with another Montana eventually and just do something differently, or whether there might be a fungal infection in the soil now.

Thank you.