I have the same problem. After some troubleshooting i’ve made a few observations. The situation is:
I’m living in a 60-somewhat apartment building. There is a Golmar Plus T-540 plus (not the SE version) hanging in my apartement. I’ve followed the instructions provided by George (only with an 1/4w resistor but that should not matter) and i’ve fed the opener a good slice of firmware 1.6.4
The first problem is that if the installation is in rest it is not possible to open the door. This causes a problem with the first step of the configuration: the ‘open door’ button is not doing anything so no command will be sent. I managed to get it sort of working by opening the connection (using the aux button) before starting the configuration.
The first few times the installation failed because no ring signal was received. Just when i got my girlfriend to help me ’ try it one more time ’ the installation was completed, and seemed to work fine.
But it didn’t work fine 
First of all not all doorbell-rings are visible in the activity log. In addition, the activity log shows ring events of some other apartments. I can hear the bell of the apartment next door and it sometimes shows up in the log, and sometimes it doesn’t. Some other events must be from other apartments but i’m not sure.
Secondly the Open function only works when there is an active (speech) connection or when that connection has been there (just hung up the horn) just before the open command is sent from the opener. NB: ringing the bell does not seem to open a connection so ring to open does not work. The only way to open the door is to either pick up the intercom horn when the bell has been rung or pick up the horn and push the ‘aux’ button (which, in my building, has been programmed to open a speech connection)
Is the Nuki capable/programmed to send the ‘open line’ command to mimic the horn being picked up? This seems to be a necessity to open the door.
If i have time i will try to hook up my logic analyser to try to reveal the secrets that the intercom has been trying to hide and share my results here.