See the dedicated subforum for the PR Series where people more familiar with that device may be able to assist and where there may be past discussions on similar issues.
https://community.wd.com/c/network-attached-storage/my-cloud-pro-series
For example there is a discussion from a few weeks ago on an SSH problem with the 2.31.193 firmware on the PR Series.
If possible try rolling back the firmware to the previous firmware version where SSH worked and see if it fixes the problem.
