#334365
The solution is to click on a perspective viewport.

If you're using the Active Shade window you can select the camera you want FIRE to render from.
If you embed your Active Shade in one of your viewports, Active Shade will always render the currently selected viewport, but keep in mind that only perspective viewports can be rendered by FIRE (or you'll get the error message you've mentioned).
#334386
You can work with Active Shade in 2 ways:

1. By having it as a floating window.
2. By embedding it in one of your viewports.

If you want it as a floating window you do the following:
a) Open Render Options (F10)
b) Select MaxwellRender as Active Shade renderer.
c) In the left of the big Render button there are 2 radio buttons. Select ActiveShade instead of Production and hit Render. A new floating AS window will pop.

Also, you can only have 1 AS window active at a time (embed in viewport or floating). Max will tell you so if you try to open 2 AS windows.
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