Tag manager won´t open

[Alvaro Hernandez]

I have a Calibre database on my google drive (cloud) which I access from multiple machines (never simultaneously).

It always (for years) worked just fine.

Today, I tried to open the tag manager (right-clicking on tag and selecting tag manager) in one of my machines and I got the following error:

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calibre, version 6.17.0
ERROR: Unhandled exception: <b>TypeError</b>:'NoneType' object is not iterable

calibre 6.17 embedded-python: True
Windows-10-10.0.19045-SP0 Windows ('64bit', 'WindowsPE')
('Windows', '10', '10.0.19045')
Python 3.10.1
Windows: ('10', '10.0.19045', 'SP0', 'Multiprocessor Free')
Interface language: None
Traceback (most recent call last):
  File "calibre\gui2\tag_browser\ui.py", line 284, in do_tags_list_edit
  File "calibre\gui2\dialogs\tag_list_editor.py", line 230, in __init__
  File "calibre\gui2\dialogs\tag_list_editor.py", line 425, in fill_in_table
  File "calibre\gui2\dialogs\tag_list_editor.py", line 390, in create_table
TypeError: 'NoneType' object is not iterable
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Tag manager is running smoothly on another machine.

I already tried uninstalling and reinstalling to no avail.

Please advise.

Tks.