gr 3.9 OOT execution error: unknown base type gr::block

[Tom McDermott]

I'm working on porting my OOT to gr 3.9  The 3.7 and 3.8 versions work fine.
The ported code is compiled and make installed.  My OOT is visible in GRC,
and
I've added to a new flowgraph.

My OOT is in category HPSDR  and the module is hermesNB (of several).

When I try to execute a simple flowgraph in GRC with this OOT I get the
following error:

Traceback (most recent call last):
  File "/home/tom/Desktop/Test_AM.py", line 38, in <module>
    import hpsdr
  File "/usr/lib/python3/dist-packages/hpsdr/__init__.py", line 18, in
<module>
    from .hpsdr_python import *
ImportError: generic_type: type "hermesNB" referenced unknown base type
"gr::block"

Do I need to add code somewhere to import gr::block   ??

Is there an issue with capitalization of  hpsdr  vs. category name of
HPSDR  ??

-- Tom, N5EG