The following url
https://dynamicdns.park-your-domain.com/update?host=root&domain=mydomain.org&password=long32characterpassword&ip=xx.xx.xx.xx
will set the DDNS at namecheap.com

I have checked it and it works via a browser. It works whether http or https is used.

So I have set up the router with the following settings:

Provider host: dynamicdns.park-your-domain.com
Service API: update?host=root&domain=mydomain.org&password=long32characterpassword&ip=###IP###
Auth Type: URL
Connection Type: Https

and I get 'Send HTTP request error'

I have also tried http rather than https with the same result.

Any suggestions please?