Ok, so something has gone haywire with the licensing system and all the pay plugins are now no activated.
I eventually was able to reactivate Feed to Post (although it won't stay activated... it keeps deactivating on it's own for some reason), by visiting my account on the website. However, I can't do that with Keyword Filtering and Full Text RSS because the Account page for those is empty so I can't deactivate to reactivate.
So, this is problematic. Aside from the above review I gave I now, unfortunately, have to say that the licensing system is a serious problem.
Anyhow, the licensing system is rendering the software completely useless.