In practice, whether you have already paid for the solution will also make a difference.
If you have not yet paid for the solution, you may not be legally obliged to pay for it until it works properly, or you may be obliged to pay only for those parts which are satisfactory (for example, functioning hardware which has been supplied). The exact position depends on the terms of the contract. The contract might even include provision for compensation.
If you have already paid, you may need to get the supplier (or a third party supplier) to repair, replace or even completely redevelop the solution, at their cost. Which of these applies will again depend on the contract. The supplier may be willing and able to sort out the problems quickly; you may have to negotiate a solution; or, in the worst case, you may need to take legal action.
