Just spent an hour or more (didn't start the clock soon enough) trying to buy an upgrade to LR 5. Found a link with the very well hidden page, trick is to change the "Buy" label to "Upgrade". You wouldn't know it was a button except by clicking on it...
Fill out the personal info, name, rank, serial number, date of birth, etc., even the CC info. Click the complete the "Sale of the Century" button and get a message that Adobe has sent me an email to "verify" the order. Great! Except for a minor problem; I haven't had that email addy for several years.
No problem, I'll just sign in (which I had already done!) and edit my account info. Super!
Except, I end up with the same message that Adobe is sending me an email to verify my identity... to the same dead, un-used, old, completely useless email address. Thought maybe I was at the Apple HQ; "Infinite Loop"!

After finding the proper phone menu, it was determined that, since I did not use CC, I would have to jump through many more hoops and use the url that was read to me very quickly. Turns out the url was not quite correct, anyway, but I managed to find a "Chat" button that was answered extremely quickly. After a few confusing I said, she said, we said, 'Baneja' said she(?) understood and in less time it takes to skin an elephant, I had a new account, and an email with a link to change my (working) password. This allowed me to sign in without having another 'dead-letter' email. I could then see that there was nothing wrong with my account emails, after all. OTOH, I think 'Baneji' had entered all that for me. However, I noticed that there was already a secondary addy that I had not mentioned to her(?). Why that one was never considered/used, I know knot!
So, what have you done lately for fun?!

BTW, here's the link for the $79 upgrade: <
Adobe Lightroom 6: How to Upgrade from LR4/LR5 for Only $79, Canonpricewatch.com> or just DuckDuckGo:"lightroom 6 upgrade for $79"