There are a number of warnings which may be issued when you enter the CAM Plot dialog. These do not prevent the output from taking place, but highlight items that you may wish to check and take action on before plotting.
Locating this option
Available from: Output menu > CAM Plots option
The Warnings
The Component Bin is not empty
With components in the Component Bin, it is possible that the design is not complete. Either the components should be placed on the board, or deleted from the bin.
Design contains Errors
The design contains error markers left by the last time the Design Rule Checker was run. Each DRC error should be reviewed and corrected before plotting.
Design has incomplete connectivity
The design contains connections which should be routed before the design is complete.