Anki isn't letting me review my green cards

When I am reviewing green cards, an error message pops up. I have copied and pasted the error message to the bottom of my post. I followed the steps on the ‘When problems occur’ page, but the error message does not go away. What should I do?

Anki 2.1.47 (dc156f34) Python 3.8.6 Qt 5.14.2 PyQt 5.14.2
Platform: Mac 10.16
Flags: frz=True ao=False sv=2
Add-ons, last update check: 2022-10-31 11:05:07

Caught exception:
Traceback (most recent call last):
File “aqt/”, line 541, in handler
File “aqt/”, line 701, in _onTypedAnswer
File “aqt/”, line 381, in _showAnswer
File “aqt/”, line 756, in _showEaseButtons
File “aqt/”, line 843, in _answerButtons
File “aqt/”, line 829, in but
File “aqt/”, line 853, in _buttonTime
File “anki/scheduler/”, line 1140, in nextIvlStr
File “anki/scheduler/”, line 1035, in nextIvl
File “anki/scheduler/”, line 923, in _nextRevIvl
TypeError: unsupported operand type(s) for *: ‘float’ and ‘NoneType’

Please follow the steps in When problems occur - Frequently Asked Questions
If issues persist, switching to the v3 scheduler may help.