I have a convertible myself, and when I bought it, it leaked in the rain pretty bad and kept leaking, with water dripping on my leg as I drove, really annoying.  Worse it was getting water inside the car where it would do damage, and it looked bad.  Fortunately, it's really quick and easy to clean, waterproof and protect a convertible top.  Here's how:

First, you want to really scrub the top with either convertible top cleaner of a fabric cleaner like lightning fast.  You want a stiff brush, I like the Hard Low Profile Tyre & Carpet Brush from rockcar 

You want the soft top really clean, so that the protectant will really soak into it.  The fabric and convertible top protectants need to penetrate into the fabric to properly waterproof the fabric, and they can't do that unless they are really clean.

Then Mist over a fabric protectant of convertible top protectant, and let dry.  You can repeat additional coats if you like.

These also work well on other fabrics, I have protected my couch, and even a hat during lockdown. 

We have included pet hairbrushes in the convertible top section, as we find cats seem to like sleeping on the roof of convertible soft tops, so if you have a convertible soft top, you will probably want a pet hairbrush as well!

Note:  We have added ValetPro's convertible top cleaners and protectants and will be upgrading the kits to these more professional products.  If your top is especially dirty though the Autostolz Convertible top cleaner is stronger, and can also be used as a general fabric cleaner.