The problem is actually being caused by a postgresql port mapping issue in the config files.
By default, Kali comes with postgres 12 (and postgres 13 as of 2020.3), but OpenVAS needs version 13. Kali configures postgres 12 to port 5532 and assigns a higher port (in this case, 5433) for postgres 13. OpenVAS is still looking for 5432 so sees postgres 12 even if 13 is installed.
remove postgresql 12 if you can...if not
A quick solution is to edit the "port = " lines in the
port = 5433
port = 5432
basically swap the port values.