How to spray paint a gazebo canopy?

Yes you can paint them provided you use the correct paint, fabric paint. I have done it but I used a roller, not a spray paint. Held up well for a couple of years before it finally died. Keep in mind I am in Zone 9 and my furniture is out year round. Never occurred to me to take photos at that time. Your husband just doesn't understand the advances in paint technology. Go ahead and paint it and he will be pleasantly surprised. Will buy you some time to save for a new canopy when the time comes too.

I have seen it. Yes it works. Just lay flat if you can, to paint and dry.

Materials that have been subjected to years of ultraviolet exposure, dirt, leaves, water, and fall out, have to be cleaned “to the max” before they will hold any new surface finish. like a paint.

Does it look horrible because of any of those things listed above? One needs to remove all dirt and one can’t remove ultraviolet damage to the fabric.

If it is vinyl, I would use an automotive-grade vinyl spray dye, from an auto parts store.

You might also try to dye it with is a synthetic fabric dye, depending on how the fabric is woven or filtered or whatever it is. That will require a big pot & hot dye bath.