System sync error

I’m attempting to request a system sync for all systems. The query part of the URL is:


In the response I get:

<sync>Missing valid systemid= parameter.</sync>

If I change ‘all’ to a numeric systemId then it works. Also, I have a separate C2 account that I use for testing, and on that the ‘all’ parameter works, so I have confidence that my code is correct.

Any ideas why the ‘all’ param wouldn’t work for just one of my accounts?