An unknown error has occured: Object reference not set to an instance of an object

If you see the error message: 

An unknown error has occured: Object reference not set to an instance of an object

It means that some files in the installation process failed to be stored correctly. To fix this you need to delete the folder where the data collector is stored. This folder is called the printer agent folder

Follow this guide: 

Step 1:

Navigate to the folder where the data collector is installation. Depending on your operating system version its located in one of the below:

c:\users\all users\printeragent

c:\users\all users\application data\printeragent

c:\appdata\printeragent

Step 2: 

Delete the folder named "Printeragent"

Step 3: 

• Install the data collector again and re-use the existing location-ID which the previous data collector used.
  
  
• Navigate to your 3manager account, go to settings, click the data collector and then copy the location ID. 
  
  
• Insert location-ID and click update.