At the moment of putting a referral code It marked error again and again?

When I did mine worked perfectly?
If you want to try mine :D
5JATM

Try to contact Fiiz by:

CHAT
Go on this page https://fizz.ca/en/faq/resolving-issues, if you are not connect login
Wait 15 seconds for the bubble icon to appear at the bottom right of the browser and click on the icon.

FACEBOOK
You can also send a message by Facebook
https://facebook.com/fizzca and click send a message (this is a bit slower)
 
FORM
You can also fill a contact form
From the panel My Profile -> Contact Form (the subjects are limited)

Try something different AQOM6 Mine works

Try to contact Fiiz by:

CHAT
Go on this page https://fizz.ca/en/faq/resolving-issues, if you are not connect login
Wait 15 seconds for the bubble icon to appear at the bottom right of the browser and click on the icon.

FACEBOOK
You can also send a message by Facebook
https://facebook.com/fizzca and click send a message (this is a bit slower)
 
FORM
You can also fill a contact form
From the panel My Profile -> Contact Form (the subjects are limited)

Try to contact fizz by chat or Facebook messenger to check

Sometimes it happens on handheld device, try to do it on your computer, less problems.

Try to erase the cache memory. G3G45

I would try entering the code manually, not copy & pasting as sometimes that leaves a space and causes an error. I do get some errors when on the Fizz website on mobile, none so far when on a desktop.

Manuel : remember that the referral code works only during the sim card activation process. Once your sim card is activated, it will be too late to use the code of your referral.

Yes as others have mentioned, using PC desktop or laptop would be better.

You can also clear cache and try incognito. Use different browser if needed.