The reason I suggested a blood pressure monitor with a memory function is so that your heart rate is recordedThe portable monitor would only take readings when I was sat down. Every time I was standing it would try to take a reading 3 times then just give up. This meant all readings looked normal. I tried explaining this but I guess it is what it is. My blood pressure isn't really a problem anyway. I do have my own monitor.
Did your GP offer you any explanation why the portable monitor wouldn't take any readings while you were standing? The failure of the monitor might suggest that you do have a problem with your blood pressure when standing.