Hello,
When printing to the Developer version from another application, a message stating that 'Printer is not ready' appear. This message is generated by Windows because printing fails.
From our side printing fails silently when printing to the Developer version from external applications.
If you think it would be nice to get an explicit message please send your suggestion to
support@amyuni.com or post it to our Wish List forum. I can't confirm if generating a message by the printer when printing fails is a good idea or not, maybe other developers prefer how things are now.