Hi ROlds, and welcome to the VMware Communities!
Which version of Fusion were you using previously? Is VMware Fusion passing it through as a USB device (with the relevant driver installed inside the guest) or as a virtual serial port (with the relevant driver installed on the host)?
If you were previously using VMware Fusion 6, you may wish to try downloading Fusion 6.0.5, which should work on Yosemite. That might provide more information about where the failure is originating.
Thanks,
--
Darius