Answer
Having two or more forces acted on an object simultaneously does not mean the object will accelerate.
Work Step by Step
When two or more forces are applied to an object simultaneously, it does not always accelerate, because even though there are forces applied to an object simultaneously, they might cancel out each other and do not create a net force as a result.
An example is when an object is tied to 2 strings in opposite directions and then pulled with equal force $F$. Even though there are 2 forces, they have the same magnitude but opposite direction, so $\sum F= F-F=0$, meaning the object in the middle will not accelerate.
