Can severe scoliosis cause overactive bladder?

Scoliosis can cause overactive bladder if it cause pressure on the sacral nerves which control both sensation and muscle coordination.
With scoliosis to the right you experience torque to the left.
I'm only answering because no one else has yet.
I have very slight scoliosis to the left and torque to the left.
Scoliotic curves tend to deepen as we age.
You might find remedy in medication to calm the bladder, pelvic floor exercise, or surgery.
If you are female a common cause of overactive bladder is pelvic organ descent.
If you are male a common cause of overactive bladder is prostate enlargement.

Medications didn’t work and trying Tadalafil seems to work at night and going to try during the day. Pelvic Floor exercise with tens unit pads between your thighs, didn’t work because they gave me sore muscles on my thighs and didn’t work with no improvement. The prostate is very low enlargement condition. So I think is due to my scoliosis.

I'm with you on the pelvic floor exercises.
You could get a lumbosacral MRI with additional forward facing images (coronal) to trace the compression of nerves by the the scoliosis. I would want to because the compression can cause irreparable nerve damage as or if if the pressure increases. It sounds like the tadalafil is relaxing the bladder.
The scare about tadalafil is the rare side effect of vision loss.