Hello, everyone!
Today, I'd like to share a case with you.
Product Model: U2000
Problem Description
Can't upgrade more than 2 devices at a time using the U2000.
Problem Analysis
The U2000 doesn't have the licenses required to do multiple software upgrades at a time.
Be sure that the U2000 has installed the licenses required to do multiple software upgrades at a time. To review the licenses Choose Administration > NE Software Management > NE Software License Management from the main menu. In the NE Software License Management window, check the license information.

If there are no licenses, a maximum of 2 devices can be upgraded at a time.
If there are licenses, a maximum of 60 devices can be upgraded at a time.
Root Cause
The U2000 didn't have the licenses required to doing multiple software upgrades at a time so by default a maximum of 2 devices can be upgraded at a time.
Solution Description
Install the respective licenses in the U2000 for can do multiple software upgrades at a time.
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