I have been running Houdini on my Gefore GTX 1660 card for the last year with no problems. Recently, all of the sudden Houdini will crash after placing only a few nodes with no error message or crash report. I have troubleshooted quite a bit and after talking if sidefx support, they said my card just isn't supported. Is the GTX 16 series really no supported? Do I really need to downgrade to have Houdini work?

That sounds like a driver update has broken something - can you either upgrade the driver again, or rollback to a previous version? Unfortunately while consumer cards are supported, they tend to cater more to games. Driver updates can be somewhat hit-or-miss.