[ivansc]

Might be worth downloading a free 64bit plug & installing that to see if it shows up.

This is definitely looking like some sort of problem with 32bit only plugins on your system. (headscratch)

One other possible hiccup. Reaper has a rule about what order it scans plugins. I cant for the life of me remember which way round it works, but if you put the 32 paths first & 64 paths second in your list, it will scan in and select one before the other, which means of you have your system scanning so the 32 bit plugs show up first, it could well be the cause of the disappearing plugins. (or it could be the other way round of course) Check it out either in the user guide or Kenny Gioia`s free video tutorial on reaper setup.

EDIT: Just had another look & it occurred to me that a few of your plugs show up as "working in 32 or 64 bit windows" which doesn't necessarily mean that the plugin itself is actually available in 32 and 64, just that the 32 bit version will work in 64bit windows!
This and the rest is the reason I now only have a couple of 32bit plugs left on my machine & one of them is based around my UAD-I cards.

Go all 64bit if you can. plenty of great free 64bit stuff out there nowadays, so very little need for the older 32 bit plugs.