WorldPing alert - no data

I’m hoping that someone could assist please.
I’m using Grafana v 6.0.1, and trying to set up an alert from a WorldPing probe ping chart, but it’s constantly reporting ‘No Data’.

In query B, I have
alias(averageSeries(worldping.$endpoint.$probe.ping.mean), 'MYaverage')
to create a series average of ping responses, and have an alias of ‘MYaverage’.

If I look at the chart, I can see ‘MYaverage’ as a series, with the expected value;
chart

The Alert is setup like this;

Yet for some reason I get the alert response as ‘No Data’???

If I ‘Test Rule’, it also confirms - ‘No Data’;

What am I doing wrong?