Which plan are you on? Apple Watch requires a special plan for it. You would not be able to use the normal plan with it

I have a normal Koodobplan for the phone. But I want to add a separate cellular plan for the watch through Koodo (5G for $10/month)

Hi ​@Bdollevoet 

Will you please let us know what iPhone model are you using?

You can check the compatible devices here https://www.koodomobile.com/en/help/smartwatch-faq

iPhone 11. Should be compatible 

Are both devices, phone and watch running on the iOS mentioned in the article above? (for the watch watchOS 11.1 or later and the iPhone must be running iOS 18.1 or later)

Yes they are. I even had this double checked with a Koodo sales guy in store. Both watch and phone are up to date with software. He doesn’t know why it isn’t working

This is an issue with Koodo, not your equipment. I spent over an hour on the phone with two different levels of technical support going through all the settings and it still didn’t connect. They have had to open a ticket with their technical support to address a system issue. I haven’t heard back from them on this yet. I’m hoping I do soon though, or I will have to call again. If that doesn’t work, I guess the only other option is changing mobile service providers.

I’m having the exact same issue.  I very clearly advised the sales rep when I purchased a second cellular package my intent; to set up an apple watch for my daughter who doesn’t own a phone.  I have the correct plan and version of the Apple Watch (2nd generation SE) however the watch tells me “The Koodo account on this Iphone cannot be used to add a cellular plan” to the watch.  Has anyone had any success getting a response from Koodo about this?