As others have mentioned. The tape needs to be just wider than the rim bed. The tyre beads need to sit on top of the tape, not next to it. Otherwise the only thing sealing the rim is the tape’s adhesive, which will fail. Personally I’d avoid gorilla tape too. It’s horrible to remove. Muc-off tape works great and is stickier and stretchier than Stan’s/tesa
The valve hole can cause leaks. I always melt the hole round by poking a hot pick through it then twizzling around. This seems to seal much much better than a cut which can spread and again cause leaking. Obviously careful with carbon rims.
The quality of the valve is another thing. The cheap basic valves with fixed rubber never work that well. The aftermarket valves with removable rubbers are so much better as the rubber is soft enough to squash meaning you can get a really good seal. For example muc-off valves have 3 different rubbers, but the thicker cone works with every rim I’ve tried. push down on the top of the valve to squash rubber and tighten up the collar. Worth investing in decent valves.