The 2020.2 release introduced the new HLS product with support for both Vitis™ and Vivado® . As part of this the overall folder structure changes, whereby the Vitis_HLS folder is now at the same root location as Vivado® and Vitis™ . You may need to update any custom setup scripts from the previous release.
The Xilinx 2021.2
settings.sh scripts will automatically handle this.