It seems the problem is that [many] people were purchasing a license that was valid for a single machine, but then applying it to multiple machines, concurrently.   Versions of MBAM prior to 3.8 "overlooked" this... but version 3.8 started checking and enforcing the one-machine license as it was intended. It is permitted to transfer that license from one system to another, by deactivating the license on the first, before activating it on the second.   It's probably for the best to set up an MBAM account, where you can register/store your license [before making the transfer]. In my case, I had two "lifetime" licenses.   The first was for beta-testing very early versions of MBAM 1.x.   If I'm not mistaken, that particular license was issued to us beta testers as a "shared" license... at least 5 people were offered the same license/registration information.   Everything worked fine for a few years, until one day, I noticed my MBAM had reverted to "free" from "premium".   I contacted MBAM, and was able to offer them "proof" of the license that I had been awarded... and so they reactivated it on my system(s).   Then, a few months ago, it happened again... my MBAM reverted.   When I tried to re-enter the same license information, it was no longer accepted. So I then tried to enter my second "lifetime" license, which I got for beta-testing very early versions of MBAE.   Fortunately, it worked. Today, I tried to register/store my license information online.   The first/MBAM license was rejected, indicating that someone else had already registered that [shared] license.   But the second/MBAE license was accepted, and is now formally registered to me.   Ironically, it's showing up as being used on two other systems that I had installed it on, but NOT on my current/primary system!
I have a lifetime license for Malwarebytes 3 (MB3) Premium on my Windows 7 system. Today an MB3 popup notified me of a FREE update to the latest version. This popup appeared legit, and similar to those in the past, so I accepted/installed it. What was installed was a time limited "trial version" of the latest MB3, version 3.8.3. It came with prompts to upgrade to (and pay for) the latest version of MB3. Just a word to the wise. If MB3 is defaulting on its lifetime licenses, ...
Malwarebytes 3 Update Oddity