Amazon WorkSpaces Client software 4.0.0 released in June 30, 2021 is the first 64-bit release of the Windows client application. In case of upgrading from an older 32-bit version 3.x it may break compatibility with some versions of FabulaTech software for Remote Desktop. This incompatibility will be fixed in the next versions of FabulaTech software. There are two workarounds to temporarily fix this issue right now:
C:\Program Files\Common Files\FabulaTech\Netlink 3\
C:\Program Files\Amazon Web Services, Inc\Amazon WorkSpaces\vchan_plugins\