This is a super old topic, but I found a fix that I thought I'd share. I also had a problem with the resolution shifting when I would move the sensor panel back to the correct monitor once it started in the wrong spot.
Edit the aida64.ini file. For me it was located here: "C:\Program Files (x86)\FinalWire\AIDA64 Extreme"\aida64.ini". You can right click on it and edit with notepad.
I had to add the appropriate sections and entries, as the didn't exist. Add the following in its own section (you need to adjust the resolution and monitor for your specific setup).
[HardwareMonitoring]
HWMonEnable=1
HWMonEnableSensorPanel=1
SensorPanelMonitor=5
SensorPanelWidth=515
SensorPanelHeight=1920
Here's where I put mine in relation to other sections, but the location shouldn't matter:
[RptLook]
ReportTheme=Auto
NFName=Verdana
NFSize=80
NFColor=0
NFBold=0
NFItalic=0
PCFName=Verdana
PCFSize=140
PCFColor=8388608
PCFBold=1
PCFItalic=0
DCFName=Verdana
DCFSize=110
DCFColor=8388608
DCFBold=1
DCFItalic=0
BGColor=16777215
[HardwareMonitoring]
HWMonEnable=1
HWMonEnableSensorPanel=1
SensorPanelMonitor=5
SensorPanelWidth=515
SensorPanelHeight=1920
[Sum]
group_computer=1
computertype=1