Could you lose a phone number after porting?

No I don't think you can get your old number back with Fizz.
Your old number still belongs to Videotron.
If your Videotron phone number is still working then you should re-try the porting process or contact Fizz and ask them to port that number for you and explain to them that it failed.

No. This is probably not possible. You can try contacting support though. Just in case, keep your videotron plan active so you have a chance to retry.
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Non, ce n'est probablement pas possible. Vous pouvez cependant essayer de contacter le support. Juste au cas où, maintenez votre forfait vidéotron actif afin de pouvoir réessayer.

Get a new sim and try again.

Is your Videotron account still active since the porting failed?

https://crtc.gc.ca/eng/phone/mobile/num.htm

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