Amanda,
This is certainly unusual.
There is nothing that unusual to the plant data query, other than the fact that it is accessing a planting specific end-point (as opposed to the multiple cloud data calls required to pull up the plant manager). So it is possible that you have a firewall, or security router, that is blocking the request, seeing it as a stray request to an unknown or un-trusted location.
Before we go down the route of trying to figure that out, I see a fairly easy thing to try as an experiment. Before clicking New for the first time, instead Edit a plant, and click the "Plant Data >" button. This accesses a web page from the plant database end-point. Then close the edit plant dialog, and try clicking New. If that works, we know that there is some sort of network monitoring, security, or policy in place. If it has no effect, we will come up with a different theory.
--J