Printer not showing it presence to Mobile devices.

I have a Brother HL-L6300DW laser printer. I recently changed my internet supplier from Vodafone to German Telekom. With Vodafone my printer was visable to my mobile devices but with my new supplier DT (German Telekom) they are not. My mobiles and TV pick up wifi from the DT router without problems.
The printer is setup to work as instructed but it doesnt show up to my mobiles. The printer "sees" the router but for some reason is not transmitting. Im sure there is a simple solution but cant find it.
Hope ive explained myself.
Thanks
John