I'm posting this because I had this problem but found no information online and hopefully this shows up in google for people who have the same issue.
I was having problems using https://github.com/qdm12/ddns-updater to update my DNS.
The error was bad request zone not found when I was trying various DynDns updating programs including the one above.
The issue is that my domains are registered on the CA ovh site and DynHost is not a feature for this region. This means that if you want to use these tools they have to implement the API not the dynamic function. If it is using the web service url "nic/update?" you are using the dynamic function.
In here the particular docker image I used has an option between dynamic and API. Dynamic is the default.
https://github.com/qdm12/ddns-updater/blob/master/docs/ovh.md
Once I switched it to API, my zones are found an able to be updated.
Are you sure that Dynhost is not implemented on the OVH Canadian hosting ?