Just wanted to note that my organization is experiencing this issue as well. It looks like the offline activation capability was seemingly removed or heavily altered within version 2020, as we've had no luck with activating that version or 2021. 2021 doesn’t even allow us to enter in a serial number and instead wants us to immediately sign-in, though that’s not possible on an internet restricted network. Version 2019 of Adobe Photoshop Elements is activating offline without any problems for us, so we're looking for a solution as well for the newer versions of this software.
Thanks, I reached out but received conflicting responses. The first agent told me to utilize the PRTK tool (Using Adobe provisioning toolkit enterprise edition), which actually seems to have worked at the moment on my one offline test PC. Unfortunately, a sign-in prompt is still displayed within 2020, and I have not tested it on 2021 editions either. Circling back to support to figure out how to get rid of the sign-in prompt, I was told that offline activation is not at all possible with 2020 or 2021, but then was told I would receive a follow up with a more appropriate and definitive answer within 24-hours about this.
In the end, the PRTK application seems promising, but it's not a solidified approach yet. Especially with the persistent sign-in prompt after the program is launched each time in an air-gapped environment.
According to the Adobe Customer Care team, the official response is as follows:
"As we have checked with the Senior Team, PRTK will not work with the Elements program. It is only for the Creative Cloud and Teams/Enterprise products. To activate the Elements 2020 or 2021 version, internet connection is needed."
So in short, while the PRTK tool seems to work in our situation as it also supports Photoshop Elements LEIDs, it likely shouldn't since we are using one-off purchased keys for Photoshop Elements. As such, the official response from Adobe is that for offline activation purposes, unless you're using Creative Cloud and Teams/Enterprise products, you need to purchase version 2019 or below.