Its likely that the website was not designed with the ability to easily turn off all buy buttons in mind and chances are that the buy button is linked to other things in a way that causes other issues elsewhere in their system.
It's certainly linked to their warehouse stock levels. When they first shut the store chances are they just manually entered 0 for all the stock values. Knowing that when they came to start up again they'd have to take a full inventory stock check before relaunch anyway - since prior to that any minor errors in stock numbers weren't a huge issue because the factory was there running to cast up replacements. They clearly can't do a manual stock check and re-entry of all that data every day. So a simple "store is shut now" policy is likely much easier for them.
It likely explains why the FW
site is still running because technically all those products are set to unavailable. Again likely awaiting a full stock take before being put back on sale - though the nature of FW
and resin likely means they don't hold much stock so they would likely only last a day or two before they'd have nothing left. So its likely better for them to wait until their reisn factory is back online.