Does the indicator light on your remote control come on when you press the Input / Source button? At first glance, this would confirm that the button is functional and transmits the signal.
Of course, you have to make sure your television has been programmed on the remote so that this button is functional. Then, there can also be several compatible programming codes for the same television manufacturer. You could try programming by code then check if the button works with everyone who has been able to turn off your TV. You will find the procedures and codes available in our support section here: https://support.videotron.com/residential/television/remote-controls/remotes-control/illico-tv-new-g...
In very rare cases, it is still possible that the function is simply not supported by your television.
Now to answer your initial question, it is possible to bring the remote control to a Videotron store to have it checked. If a defect is confirmed on the spot and your terminal is rented or still covered by a warranty, it will be replaced at no charge.