Some devices can not connect

We use the cloud hosted cnmaestro. 99% of our devices are connected just fine but a few of them are stuck at "connecting" and show off line in cnmaestro.

Here is an example:

But if I ping the cnmaestro server, it works just fine:

I have re-entered the cloud credentials, rebooted the AP, nothing seems to shake it loose...  This is an SM running 3.5.6.  We have a 1000 AP and another SM (connected to it) also doing this.