PayPal recently - around 28 Jun 2018 - changed some of their security settings. Their servers and my web hosting company are no longer playing nicely together, so WinXX keys are no longer generated automatically.
Credit card transactions - those that do not go through PayPal - are not affected.
I didn't discover this until this past weekend. As of this morning (31 Jul 2018), I've manually generated and sent keys for all affected transactions.
A couple of people tried registering again (vial PayPal) when they didn't immediately receive a key - those "extra" transactions have been refunded.
I apologize for the delays and lack of response to emails. My only defense (and it's not a very good one) is that I get so many "I lost my key" emails every week that my eyes glaze over when I see "WinXX" and "key" in a subject line... and I end up passing right over the email.
I've changed the "paypal" scripts on my site to do two things:
* warn that PayPal registrations might take a couple of days to get a key
* send me a very specific email telling me that I need to manually generate a key
Again, my apologies for the delays in getting keys sent and, especially, the lack of timely response to emails about those missing keys.