I've spent a bit of time looking into this and ensuring that the sitemap of all Voice websites is loading correctly, in Google's search console.
Currently Google are reporting that your site is Discovered - currently not indexed.
Google's documentation says this means that: The page was found by Google, but not crawled yet. Typically, Google wanted to crawl the URL but this was expected to overload the site; therefore Google rescheduled the crawl.
Elsewhere in the search console, Google reports that it has had no problems with crawling the Voice site in the last 90 days. So I don't think there's any problem on the Voice side that has caused this. I guess it was just busy crawling lots of other pages on Voice sites and decided that crawling your site at that moment would have been too much!
I have specifically asked for the site to be indexed and it says that it's been added to a priority queue, and also that there are apparently no problems with loading the page. So I guess we just have to wait!
There are a few other Voice sites in this same state, though only a very small percentage of the total number of sites. The vast majority are crawled and indexed.
I'll keep an eye on the info in the search console over the next few days/weeks to see if the situation changes.
Joe - Voice Admin