A standard silicone suction cup has to be just as clean as the surface you attach it to. Clean with dish soap and water and let air-dry. You mentioned a textured mounting surface. You have two options. Attach a mount base, a flat disc, to the dashboard and attach the suction cup to that base. There are two types of mount base. One has double-sided adhesive and is one-time or permanent use and the other type has a sticky gel pad that is reusable. The latter is more expensive. There are also suction cups that have gel-like surface and they will stick to textured surfaces. This is in my opinion the best solution. Search for gel suction cup phone mount.