Extensions Vanishing from Firefox Portable

For some reason after installing FFP and adding No Script Security Suite and HTTPS Everywhere extensions, and then browsing with both extensions working fine, upon restarting Firefox the next browsing session, all my extensions were gone. A search in the installation folder turned up nothing recognisable. I installed both extensions again, and again, upon restarting Firefox, both were gone. The issue may not be peculiar to FFP. Shortly before installing the Portable Apps version, I installed Firefox full (version 53), and found these two extensions and a number of others were all being refused by Firefox as signature fails. Nonetheless, they installed fine when I dropped Firefox and installed the portable version - then vanished. And then vanished again.

Has anyone had this happen?