Adobe Acrobat DC 2015 License issue

[Matt B12345]

I have a volume license for Acrobat DC 2015 that I have been using for the last 8 years.  We have it installed on approximately 40 computers and have a 50 license pack.  Adobe has verified that my serial number is active and valid, however we receieve the below pop up each time Acrobat is opened.

If I continue it fails, however I can close the pop up and continue working.  It comes back every few minutes and with each document opened.  

[Abambo]

As you have 50 licences, on how many computers did you install the licences? Did you before uninstalling, sign out the licence?

[Matt B12345]

Over the years, it has been installed more than 50 times, but its currently installed on approximately 40 workstations or servers.  I never logged out when retiring a computer and it worked just fine until yesterday when we started receving this message.

[try67]

I guess they found out about it and blocked you from further exceeding your seat limit. You must deactivate/log out from any computer you want to retire! Maybe there's a way to deactivate all current seats and then re-activate them, though. You'll need to ask Adobe's enterprise support about that.

[Matt B12345]

I spent several hours on the phone with support.  They said the license was not blocked in their system and they do not show a count of the total activations.  Adobe enterprise support suggested I go to the forums because they are unable to assist with the older versions.  Just looking for any possible ideas to get past this message.  It seems more like a bug than an issue with the license as it shows the same number of days, 32767, which is approximately 90 years. 

[Abambo]

It seems more like a bug than an issue with the license as it shows the same number of days, 32767, which is approximately 90 years. 

By @Matt B12345

Sure, it may well be a bug appearing only when installing the old software on a newer (unsupported) OS. That's the risk to take.

To be clear, the error could have originated anywhere between your system and Adobe. What Windows are you using?

[Matt B12345]

Windows 10, 11 and Server 2016, 2019

[Abambo]

Over the years, it has been installed more than 50 times, but its currently installed on approximately 40 workstations or servers.  I never logged out when retiring a computer and it worked just fine until yesterday when we started receving this message.

By @Matt B12345

You may have hit the magic number of activations yesterday.

[Matt B12345]

No new computers have been activated in several months and Adobe support confirmed the license was okay.

[Matt B12345]

When I try to activate, I receive the following

[BradDrumz]

Any updates? I am having the same issue with Acrobat DC 2015. But I have not done any installs for this version. The user reported this issue out of the blue and getting both messages you have attached.

[Matt B12345]

Unfortunately I don't have a single useful update.  I have spent several hours on the phone with support, but they are limited because the product is no longer supported.  I will make sure I update the post if I find a solution.