3CX v11 with GXP2120 (ext 100) & GXP2110 (ext 200) & GXP1200 (ext 201) 100 & 200 are in a ring group I have the option to receive multiple calls checked in each ext. When I set up a call between ext 100 & 200 (both off hook as though talking to each other) and dial 100 or 200 from 201 the 2nd line key flashes as it should. The trouble is when I dial the ring group 800 there are in I get a busy tone. I have checked the Line 1 & 2 key settings in each phone they are set to use the same account. The line keys do work if I dial the ext 100 or 200 from 201. Can anyone please tell what I am missing?