I just figured out an issue with my wirelessly networked Brother printer. It may be the same thing affecting you.
When I added a printer using the Printer app under Administration, it finds my printer, installs the drivers, and says it is installed, but it will not print.
The issue is the Device URI not resolving properly. I don't know why.Here is how I resolved it.
1. Figure out what the IP address is of the printer. (I logged into my router and viewed the "connected devices" to find the IP address assigned to my network printer, but there may be an easier way). In my case it was 192.168.1.10, but yours will likely be different.
2. Open up the Printer app, right click on the printer (that is installed but not printing), and select "Properties".
3. If you have the issue I have, then the field "Device URI" will say something like: lpd://BRW00234D70A462/BINARY_P1
Change the host to the IP address you determined in step 1. So it looks something like: lpd://192.168.1.10/BINARY_P1
4. Hit "Apply" and hope the test page works!!