Exile360, thank you for your reply.
I contacted Malwarebytes Support by email, and they essentially told me the same thing.
However, regarding the number of devices, when I first installed Malwarebytes years ago it allowed installation on up to 5 devices simultaneously, including PCs and Android phones. Once I purchased the license, I was able to apply it to all the devices and I’ve been doing that since then without any issues. Previously, I had probably deactivated the license on old devices before trying to activate it on a new one, except this time I am unable to access my old PC (crashed) and phone (returned, although I had done a factory reset, which I assume deactivates licenses).
Maybe I just got lucky (I thought it was a great deal).