User defined Dynamic DNS / URL Update not working on XMG3927 router

Digitallife

Model: XMG3927-B50A

Firmware: V5.17(ABMT.6)C0

I am fresh and proud owner of the zyxel router XMG3927-B50A. Besides this I also own a domain. However I dont posses a static ip and I need to rely on DDNS services.

For hosting purposes I want to update my dynamic ip on my domain over the routers own dynamic DNS feature.

My domain registrar wants a request in this format:

https://registrar.com/nic/update?hostname=[DOMAIN]&myip=[IP]&username=[USERNAME]&password=[PASSWORD]

My educated guess is, that [] should be tokens which get extracted from the set parameters in the zyxel gui for an example [DOMAIN]==test.example.ch

Now whatever combination I try I never can get the User authentitifaction request to be accepted.

I tried various combinations of tokens like _ _ or % % and I even hardcoded all of the requested informations but to no succes.

Example hardcoded request:

https://registrar.com/nic/update?hostname=test.example.ch&myip=1.2.3.4&username=test&password=test3

My suspicion is, that even when everything is hardcoded the router will add to the URL wrongly fromated informations like the set hostname in the gui. I guess if I would have the right syntax for tokens on this router I might get this runing.

My questions are:

1. Is there a specific syntax for tokens I need to follow for this?
2. Has anyone got a user defined DDNS request working on this router?
3. Is this feature bugged?

Any infromation or help is much appreciated!