This is such a common problem that Aosu has their own guide for it:
If possible, try to bring a battery bank to those cameras and have them charge off of those.
I live in Canada and have two solar cameras. One of them has the panel mounted very high with zero obstructions. It’s charging completely even now in late December.
Unfortunately, the same cannot be said of the other camera. It’s always been slightly obstructed, but overcast conditions, limited daylight and overhanging shadows from nearby buildings means it’s been struggling to charge via solar since late November. Thankfully, this one’s very easy for me to take down and recharge in-doors, which I did about ~2 weeks ago. I suspect I’ll have to do that at least one more time this season.