What are the common causes of ArcGIS Pro disconnected from ArcGIS Online?

[JonKwong1]

I have an ArcGIS Pro instance hosted in AWS, which is being used to run some arcpy scripts on a regular basis. I want to setup high availability by setting up a 2nd instance cloned from the 1st instance. 

Naturally, I would setup the two instances to connect to a license manager also hosted in AWS. I understand that concurrent use license is not supported in cloud environment until recently, as documented in this white paper https://downloads.esri.com/support/downloads/other_/arcgis_desktop_licensing_in_cloud_environments.p....

In the document, it also explains that for named user license, a single user may login on up to 3 simultaneous devices. So, does it mean that I can setup HA by having both ArcGIS Pro instances login to the same name user in ArcGIS Online? This is good news as I won't have to maintain another machine to host the license manager.

I wish to have the instances run for months without the need for human intervention. However, I am concern about ArcGIS Pro disconnected from ArcGIS Online. I know the common reasons this probably happened are; someone revoked the license or the password has changed. Are there other reasons that ArcGIS Pro will get disconnected from ArcGIS Online?

For my use case, is named user license a valid alternative to concurrent use license?

[AmnoyAm]

With the Named User licensing option, you can log into to Pro on up to three separate system.  Although I'm not sure if it was meant to be used in your scenario, but it is technically possible.  

As for your other concern about a disconnect from AGOL, this is not different than Pro running on any other system.  There are three possible issues where Pro can fail:

   1.    AGOL goes down.

   2.   The system where Pro was installed goes down.

   3.  Network related issues.

The chances of any of the above issues occurring is very low and no more higher than Pro installed on any other system or any other licensing option.